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Journal articles on the topic 'High frequency ultra-sound'
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1
Makler, S. S., D. E. Tuyarot, E. V. Anda, and M. I. Vasilevskiy. "Ultra-high-frequency coherent sound generation in resonant tunneling." Surface Science 361-362 (July 1996): 239–42. http://dx.doi.org/10.1016/0039-6028(96)00393-7.
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Fisher, Clare, Francis Duck, Christopher Branford-White, and William Whish. "The Effect of High Frequency Ultra Sound on Cell Adhesion." Biochemical Society Transactions 24, no. 1 (February 1, 1996): 122S. http://dx.doi.org/10.1042/bst024122s.
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Greenaway, M. T., A. G. Balanov, D. Fowler, A. J. Kent, and T. M. Fromhold. "Using sound to generate ultra-high-frequency electron dynamics in superlattices." Microelectronics Journal 40, no. 4-5 (April 2009): 725–27. http://dx.doi.org/10.1016/j.mejo.2008.11.051.
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Schmidt, Felix N., Maximilian M. Delsmann, Kathrin Mletzko, Timur A. Yorgan, Michael Hahn, Ursula Siebert, Björn Busse, Ralf Oheim, Michael Amling, and Tim Rolvien. "Ultra-high matrix mineralization of sperm whale auditory ossicles facilitates high sound pressure and high-frequency underwater hearing." Proceedings of the Royal Society B: Biological Sciences 285, no. 1893 (December 12, 2018): 20181820. http://dx.doi.org/10.1098/rspb.2018.1820.
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The auditory ossicles—malleus, incus and stapes—are the smallest bones in mammalian bodies and enable stable sound transmission to the inner ear. Sperm whales are one of the deepest diving aquatic mammals that produce and perceive sounds with extreme loudness greater than 180 dB and frequencies higher than 30 kHz. Therefore, it is of major interest to decipher the microstructural basis for these unparalleled hearing abilities. Using a suite of high-resolution imaging techniques, we reveal that auditory ossicles of sperm whales are highly functional, featuring an ultra-high matrix mineralization that is higher than their teeth. On a micro-morphological and cellular level, this was associated with osteonal structures and osteocyte lacunar occlusions through calcified nanospherites (i.e. micropetrosis), while the bones were characterized by a higher hardness compared to a vertebral bone of the same animals as well as to human auditory ossicles. We propose that the ultra-high mineralization facilitates the unique hearing ability of sperm whales. High matrix mineralization represents an evolutionary conserved or convergent adaptation to middle ear sound transmission.
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Miura, Syumpei, Kenta Iwai, Yoshiharu Soeta, and Takanobu Nishiura. "Upper hemisphere sound image control with horizontal-arranged loudspeakers based on parametric head-related transfer functions." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 5 (August 1, 2021): 1072–82. http://dx.doi.org/10.3397/in-2021-1749.
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The 22.2 multichannel sound system has been developed for an ultra high-definition television system. This system consists of twenty two loudspeakers and two sub-woofers called low frequency effects, and can reproduce three-dimensional sound image appropriate to the ultra high-definition television system. However, this system has a problem of high cost to install. On the other hand, the multichannel sound system with horizontal-arranged loudspeakers has lower cost to install than full scale one. However, this system cannot reproduce an upper sound image. Therefore, in this paper, we propose the upper sound image control with horizontal-arranged loudspeakers based on the parametric head-related transfer functions. The proposed method generates binaural signals to control the sound image elevationally based on the parametric head-related transfer functions in the median plane. Also, the proposed system uses the interaural level difference to control the sound image of binaural signals azimuthally. Finally, the proposed method generates output signals for horizontal-arranged loudspeakers from binaural signals by designing a multichannel inverse system based on multi-input / output inverse theorem. The experimental results show that the proposed method can control the sound image to elevation angle with the same accuracy as binaural lreproduction. The 22.2 multichannel sound system has been developed for an ultra high-definition television system. This system consists of twenty loudspeakers and two sub-woofers called low frequency effects, and can reproduce three-dimensional sound image appropriate to the ultra high-definition television system. However, this system has a problem of high cost to install. On the other hand, the multichannel sound system with horizontal-arranged loudspeakers has lower cost to install than full scale one. However, this system cannot reproduce an upper sound image. Therefore, in this paper, we propose the upper sound image control with horizontal-arranged loudspeakers based on the parametric head-related transfer functions. The proposed method generates binaural signals to control the sound image elevationally based on the parametric head-related transfer functions in the median plane. Also, the proposed system uses the interaural level difference to control the sound image of binaural signals azimuthally. Finally, the proposed method generates output signals for horizontal-arranged loudspeakers from binaural signals by designing a multichannel inverse system based on multi-input / output inverse theorem. The experimental results show that the proposed method can control the sound image to elevation angle with the same accuracy as binaural reproduction.
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Aurégan, Yves. "Ultra-thin low frequency perfect sound absorber with high ratio of active area." Applied Physics Letters 113, no. 20 (November 12, 2018): 201904. http://dx.doi.org/10.1063/1.5063504.
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Choi, Kyoung-min, Jang-Seok Park, Se-min Oh, Hunyoung Jung, and Jungho Ryu. "Study on acoustic properties of ultra-low-density polyurethane with Nano-Cellulose." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, no. 7 (November 30, 2023): 1329–33. http://dx.doi.org/10.3397/in_2023_0197.
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Recently, polyurethane materials are commonly used as engine room sound-absorbing materials to reduce the weight of automobiles. Polyurethane materials have excellent sound absorption performance in the 800~2,000 Hz frequency range due to the structural characteristics of the material, but the sound absorption performance of more than 2,000 Hz is insufficient. In the case of electric vehicles, it is important to improve the high frequency noise generated by the motor, and the need for modification of polyurethane materials has increased. High frequency performance can be improved by improving the air permeability of polyurethane cells through the bonding structure of polyurethane materials, optimization of blowing and gelling reactivity, and the amount of foaming gas. Increased air permeability of polyurethane materials reduces density and strength. In this study, Nano-cellulose is a highly functional new material with light and high mechanical properties through a chain bundle structure. The dispersibility is improved by optimizing the content and particle size of nano-cellulose. The goal is to develop ultra-low-density polyurethane with excellent sound absorption performance in high frequency areas over 2,000 Hz and improved strength. The strength of hood insulation and dash outer products can be improved by applying the developed polyurethane material. In addition, the quality of lightweight engine room sound absorbing materials for electric vehicles can be improved.
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Chen, Yuanling, Yaguang Jin, Qiang Wan, and Yuan Liu. "Study on fault diagnosis of ultra-low-speed rolling bearings based on full vector sound spectrogram." Insight - Non-Destructive Testing and Condition Monitoring 65, no. 4 (April 1, 2023): 209–16. http://dx.doi.org/10.1784/insi.2023.65.4.209.
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By exploring the mapping relationship between the multi-directional data and fault characteristics of bearings, a time-frequency analysis method for considering the multi-directional acoustic emission (AE) data of bearings is proposed. Firstly, using the full vector spectrum (FVS) theory, the full vector sound spectrogram of the dual-channel AE signal of a bearing is extracted to enhance the representation of the fault state using time-frequency characteristics. Then, the obtained full vector sound spectrogram is transformed into a specific size as the input feature map and a convolutional neural network (CNN) classifier model is established. Next, the Softmax classifier is used to classify the bearing faults in order to realise the intelligent fault diagnosis of an ultra-low-speed rolling bearing. The comparison of the different models shows that the average recognition accuracy using the full vector sound spectrogram CNN model can reach 95.61%, which is better than the other three methods. The feature extraction using the full vector sound spectrogram feature analysis method has a high degree of recognition for bearing faults in an ultra-low-speed state and can provide high accuracy and stability under noisy conditions.
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Cheng, Y., C. Zhou, B. G. Yuan, D. J. Wu, Q. Wei, and X. J. Liu. "Ultra-sparse metasurface for high reflection of low-frequency sound based on artificial Mie resonances." Nature Materials 14, no. 10 (August 31, 2015): 1013–19. http://dx.doi.org/10.1038/nmat4393.
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Tang, Jianfang, Minghao Hu, Gan Jiang, Xuanyu Zheng, and Fei Peng. "Airborne Sound Sensing System Based on DAS and Ultra-Simple Transducer Structure." Photonics 9, no. 12 (December 12, 2022): 975. http://dx.doi.org/10.3390/photonics9120975.
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Fiber-distributed optical fiber acoustic sensor (DAS) is generally used in distributed long-distance acoustic/vibration measurement. Recently, DAS is also used in weak airborne sound detection. To improve the sensitivity of DAS, using a state-of-the-art acoustic transducer or a special enhanced scattering fiber, which are uncommon in the industrial site, is often essential, according to the previous research. In this work, the fading of DAS is suppressed by the multi-frequency probes and polarization-diversity-receiver scheme. The self-noise of DAS is further lowered by the phase averaging of multiple acoustic channels wound on the transducer. We found that, supported by this high-performance DAS, even if the transducer is made with an ultra-simple plastic structure in daily life, the system can achieve high-sensitivity airborne sound sensing. The proposed simple acoustic transducer can reach the sensitivity level of −106.5 dB re. 1 rad/μPa at a sensing range of 5.1 km, which can meet many demands on the industrial site.
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Zhu, Yuanzhou, Houyou Long, Chen Liu, Haixiao Zhang, Ying Cheng, and Xiaojun Liu. "An ultra-thin ventilated metasurface with extreme asymmetric absorption." Applied Physics Letters 120, no. 14 (April 4, 2022): 141701. http://dx.doi.org/10.1063/5.0086859.
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Recent progress in minimizing sound absorbers is driven by their great scientific significance and engineering value; however, compact devices for low-frequency sound are still challenging. Here, we construct an ultra-thin metasurface by parallel connecting resonators with high dissipation loss to a non-resonant reactance-dominated boundary (RDB) with high radiation loss, which realizes extreme absorption asymmetry at the exceptional point of scattering eigenvalue. We develop a parallel transfer matrix method to design the system, and a deep-subwavelength absorber (the operating wavelength is 120 times of its thickness) with 99.2% and 0.5% absorption for sound incident from opposite ports is achieved. The extreme absorption asymmetry is ascribed to the distinct coupling between the RDB and resonant meta-atom in an unbalanced dissipating state with excellent robustness against geometrical reconfigurations originated from the broadband near-unity reflection characteristics of the RDB. In particular, the proposed strategy brings the design of a degree of freedom rather than typical multiple resonant modes, and an extensible prototype showing >90% (<1%) absorptance for left- (right-) incidence within a wavelength from 23.3 to 18 times its thickness is demonstrated.
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Glyva, Valentyn, Oleksandr Zaporozhets, Larysa Levchenko, Nataliya Burdeina, and Vasyl' Nazarenko. "Methodological Foundations Protective Structures Development for Shielding Electromagnetic and Acoustic Fields." Strength of Materials and Theory of Structures, no. 110 (June 26, 2023): 245–55. http://dx.doi.org/10.32347/2410-2547.2023.110.245-255.
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In many cases the simultaneous protection against electromagnetic and acoustic fields of wide frequency ranges is required. The complexity of such a task lies in the impossibility of significantly reducing low-frequency sound levels with traditional sound-absorbing materials, as well as the different requirements for materials that shield low-frequency and high-frequency electromagnetic fields. It is proposed to solve this problem by creating a two-layer structure, the front surface of which is solid, and the inner surface is perforated. The front panel can be made of non-conductive material. It is a variant of the Bekeshi panel and is mainly intended to reduce the level of low-frequency sound of a certain frequency with high amplitude. The perforation of the internal (metal) panel is chosen based on the need to provide shielding of electromagnetic and acoustic fields of certain frequencies or frequency bands. A calculator is provided for calculating the required panel parameters (linear dimensions, thickness, hole diameters, their number per unit of surface area). It is advisable to fill the space between the panels with a sound-absorbing material, for example, granulated polystyrene. It provides sound absorption of medium and high frequencies and makes the design broadband. The use of ferromagnetic material of the inner panel provides protection against the magnetic component of the ultra-low frequency electromagnetic field (mainly industrial). The perforation of the panel is calculated based on the waveguide theory of high-frequency electromagnetic waves. The results of tests of the effectiveness of facing metal-polymer material in the form of tiles are presented. The performance of the material is satisfactory for most industrial and domestic conditions. Determination of the mechanical properties of the material (Young's modulus, shear modulus and Poisson's ratio) showed that it is not inferior to known materials even with a large content of shielding substance. In order to rationalize the design of the structure, a priority factor and frequency (frequency band) is selected on the basis of live measurements of the electromagnetic and acoustic spectra. It is shown that the calculations have large volumes, and the solution of two-factor optimization problems is not always possible. Appropriate creation of application software to simplify the process of designing protective structures and rationalizing panel parameters based on the principles of reasonable sufficiency.
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Qian, Yu Jie, Ke Cui, Shu Mei Liu, Zi Bo Li, De Yi Kong, and Shao Ming Sun. "Development of Broadband Ultra Micro-Perforated Panels Based on MEMS Technology." Applied Mechanics and Materials 535 (February 2014): 788–95. http://dx.doi.org/10.4028/www.scientific.net/amm.535.788.
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Fabrication process of ultra micro-perforated panels (ultra-MPPs) with perforations of diameter below 100 um based on MEMS technology is expatiated in this paper. As a promising alternative to the conventional porous absorbing materials, MPP absorber is now being widely used in noise control engineering. Theory reveals that the maximum sound absorption bandwidth of a single MPP absorber could be achieved by reducing the perforation diameter to a certain limit and the desirable perforation diameters are less than 100um under many circumstances. However, due to the limitation of traditional manufacturing tools and techniques, MPPs with ultra-micro perforations of diameter less than 100um, namely for ultra micro-perforated panel (ultra-MPPs), have seldom been investigated yet. In this study, micro electro mechanical systems (MEMS) technology was applied to a trial production of ultra-MPPs and the measurement of their normal absorption coefficients were carried out in the impedance tube. Results show that ultra-MPPs could attain high absorption over a broad frequency range, indicating that as a micro machining process, MEMS technology is suitable for fabricating ultra-MPPs in order to ensure the absorption performance.
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Ketten, Darlene R., Andrea M. Simmons, and James A. Simmons. "Bats to belugas: Functional anatomy of air versus water biosonar." Journal of the Acoustical Society of America 153, no. 3_supplement (March 1, 2023): A94. http://dx.doi.org/10.1121/10.0018280.
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Acoustic task similarities of odontocetes (toothed whales) and microchiropterans (insectivorous bats) suggest they have common biosonar mechanisms. However, media differences; e.g., sound speeds in air versus water, may have driven variations in auditory system adaptations. We examined the peripheral auditory system of an FM bat (big brown bat Eptesicus fuscus) and two toothed whale species (harbor porpoise Phocoena phocoena; bottlenose dolphin Tursiops truncatu) using ultra high resolution (11 μm) isotropic voxel microCT. Significant differences were found among species for oval window location, cochlear length, basilar membrane gradients, cochlear spiral morphometry, cochlear curvature, and basilar membrane stiffness. High and low frequency hearing range cut-offs correlate with basilar membrane thickness/width ratios and cochlear radii of curvature. These features predict species specific high and low frequency hearing limits. Harbor porpoises, the highest frequency echolocator in the study, have large basal basilar membrane ratios and a “foveal” region with a constant membrane ratio similar to those reported for some bat species, consistent with a “stretched” frequency region. Furthermore, both the bats and harbor porpoises examined displayed unusual stapedial input locations and tightly coiled cochleae, specializations that may enhance ultrasonic frequency signal resolution and diminish low frequency cochlear propagation.
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Taufiq Zaliran, M., Anika Zafiah M. Rus, Shaharuddin Kormin, and M. Shafiq M Azahari. "Development and Characterization on sound acoustic at photo-induced polymer foam composited at prolonged ultra-violet exposure." International Journal of Engineering & Technology 7, no. 4.33 (December 9, 2018): 479. http://dx.doi.org/10.14419/ijet.v7i4.33.28159.
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In this paper, polymer foam composites (FC) have been developed based on polyol mixed flexible crosslinker and fibre filler of Meranti Merah. 10 mm, 20 mm and 30 mm thickness of foam polymer and its composites have been use in this study. The percentage loading of wood fibre of 5%, 10%, 15% and 20% added with polymer foam is namely as polymer foam (PP) and its composites of PP5, PP10, PP15 and PP20. The sound absorption coefficient (α) and pore structure of the foam samples have been measure by using Impedance Tube test and Scanning Electron Microscopy (SEM). UV Weatherometer is used to examine the durability and weatherproof of its composite. The results show that the highest thickness of the highest percentage fiber filler (Pp2030) gives higher sound absorption coefficient (α). 0.9922 and 0.99889 which contributed from low and high frequency absorption level respectively. The smallest pores size structure was observed with highest filler loading of PP20. The higher the thickness and the higher the percentage loading of wood filler gives smaller pore structure, consequently, increased the sound absorption coefficient level. Meanwhile, the stability of polymer foam composites is high due to unchanged pore structures morphology with prolonged ultra violet exposure.
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Rajaram, Shankar, and James Tuman Nelson. "High-Performance Floating Slab Track: Design and Construction Improvements Based on Lessons Learned from Prototype Slabs." Transportation Research Record: Journal of the Transportation Research Board 2673, no. 1 (January 2019): 300–309. http://dx.doi.org/10.1177/0361198118823004.
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The Northgate Link extension of the Sound Transit’s Link light-rail transit system subway tunnels under the University of Washington must meet stringent vibration thresholds as agreed between Sound Transit and the university to protect vibration-sensitive research labs. To meet the vibration thresholds the design team developed a 5 Hz floating slab track with an ultra-straight rail as the appropriate solution. Considering that such a solution pushes the engineering envelope, a 440-foot prototype section with 5 Hz floating slab track and a 1000-foot section of un-isolated track with milled rail were installed in the University Link tunnels to test the design. The performances of both prototype sections were evaluated during pre-revenue service and revenue service of the University Link. Based on the performance evaluation, the design of the floating slab track was refined, and the construction tolerances were tightened. The design refinements focused on improving vibration isolation performance, including stiffer rail fasteners, slightly softer support pads, and slightly heavier slabs. The construction specifications included limits on rail undulation consistent with European standards for high-speed track, EU Type 1 rail welding standards, and implementation of a frequency response pass/fail criteria on the installed slabs. This paper provides the details of the design changes, the construction tolerances, and preliminary performance results.
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Varanda, Brenno R. "Testing and modeling of nozzle and eartip acoustics for balanced armature tweeter implementation in earphones." Journal of the Acoustical Society of America 153, no. 3_supplement (March 1, 2023): A37. http://dx.doi.org/10.1121/10.0018066.
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Balanced armature (BA) receivers can be used as tweeters in earphones to increase their treble and ultra sound bandwidth. Key factors that influence the 9–20 kHz response of earphones when implementing BA tweeters are shown through experimental validation and comparison to newly-developed SPICE lumped parameter models (LPM). While the BA location and acoustic passage inside the earphone are important factors, the study focuses on how changes to the design of the earphone’s nozzle and the choice of ear-tips affect the 9–20 kHz frequency response. Improvements to existing SPICE LPM elements are provided, based on finite element analysis of the acoustic passageway that is formed between the compressed eartip and ear-simulator couplers. The model is compared to measurements from various nozzle and eartip configurations, validating its effectiveness to capture the earphone’s high frequency response due to changes to the earphone’s nozzle and eartip geometry.
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Xiao, Zhenqian, Penglin Gao, Dongwei Wang, Xiao He, Yegao Qu, and Linzhi Wu. "Machine learning assisted design of acoustic metamaterials with broadband sound-absorbing and superior mechanical performance." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, no. 4 (November 30, 2023): 4943–49. http://dx.doi.org/10.3397/in_2023_0701.
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It remains challenging to design lightweight metamaterials with superior sound-absorbing and load-bearing capacities. One promising approach is using multiple coherently coupled resonators to serve as sound absorbers and reinforced grid cores of sandwich panels. However, with too many design parameters each requiring careful tuning to reach the stringent critical coupling condition, achieving an optimal design based on experience alone is challenging. An autoencoder-like neural network is constructed that, once well trained, significantly promote the inverse design process thanks to the highly efficient computational speed. Particularly, a probabilistic model is inserted into the network to tackle ill-posed inverse problems requiring man-made and probably unreal spectrum as an input, and can provide multiple ultra-thin (32 mm) and broadband designs. We have fabricated and tested the optimized metallic sandwich structures, showing broadband capacity of using solely nine resonators to achieve quasi-perfect sound absorption (over 0.9) from 399 to 675 Hz. The static compression and dynamic impact testing also verify the superior mechanical performance with high yield strength (21.2 MPa) and large normalized energy absorption (0.29) at lower relative density (13.5%). We believe this work is encouraging to accelerate the design of multifunctional absorbers targeted especially for low-frequency noise control in engineering.
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Cai, Chenglin. "The applications of sonar and radar systems in underwater detection." Applied and Computational Engineering 37, no. 1 (January 22, 2024): 254–58. http://dx.doi.org/10.54254/2755-2721/37/20230519.
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The development of sonar and radar systems utilizing sound and radio waves, respectively, has evolved significantly over the past two centuries. Recent decades have witnessed remarkable progress in remote sensing using high-frequency Doppler radars for marine surface parameter analysis. Understanding animal behavior around sustainable ocean energy sources is crucial for mitigating potential risks linked to such installations. Increasing the Signal-to-Noise Ratio (SNR) enhances signal reception. A technique estimating noise in the detection coil's first half determines the transfer function between the reference and detection coils. This enables separation of the Ultra-Nuclear Magnetic Resonance signal from noise, preserving it using non-linear fitting. Sonar systems, using sound waves, detect underwater objects, map surfaces, and track marine life. Sound waves emitted by the transmitter are reflected back to calculate distances. Challenges in sonar systems include a blind zone caused by submerged transducers in shallow water. To improve, SNR enhancement is critical. Sonar's future may rely on AI-assisted signal processing. Radar systems, operating with radio waves, share features with sonar, focusing on object detection and ranging. Improvement avenues include 3D imaging and AI-enhanced signal processing. In conclusion, sonar and radar systems are crucial tools for underwater exploration and object detection. While challenges persist, innovative solutions and AI advancements promise enhanced capabilities for both systems.
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Wu, Gexuan, Jianlong Wei, Shuai Wang, Guangshun Wei, and Bing Li. "A 34.7 µW Speech Keyword Spotting IC Based on Subband Energy Feature Extraction." Electronics 12, no. 15 (July 31, 2023): 3287. http://dx.doi.org/10.3390/electronics12153287.
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In the era of the Internet of Things (IoT), voice control has enhanced human–machine interaction and the accuracy of keyword spotting (KWS) algorithms has reached 97%; however, the high power consumption of KWS algorithms caused by their huge computing and storage requirements has limited their application in Artificial Intelligence of Things (AIoT) devices. In this study, voice features are extracted by utilizing the fast discrete cosine transform (FDCT) for frequency-domain transformation and to shorten the process of calculating the logarithmic spectrum and cepstrum. The designed KWS system is a two-stage wake-up system, with a sound detection (SD) awakening KWS. The inference process of the KWS network is achieved using time-division computation, reducing the KWS clock to an ultra-low frequency of 24 kHz.At the same time, the implementation of a depthwise separable convolution neural network (DSCNN) greatly reduces the parameter quantity and computation. Under the GSMC 0.11 µm technology, post-layout simulation results show that the total synthesized area of the entire system circuit is 0.58 mm2, the power consumption is 34.7 µW, and the F1-score of the KWS is 0.89 with 10 dB noise, which makes it suitable as a KWS system in AIoT devices.
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Håkansson, Jonas, Cathrine Mikkelsen, Lasse Jakobsen, and Coen P. H. Elemans. "Bats expand their vocal range by recruiting different laryngeal structures for echolocation and social communication." PLOS Biology 20, no. 11 (November 29, 2022): e3001881. http://dx.doi.org/10.1371/journal.pbio.3001881.
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Echolocating bats produce very diverse vocal signals for echolocation and social communication that span an impressive frequency range of 1 to 120 kHz or 7 octaves. This tremendous vocal range is unparalleled in mammalian sound production and thought to be produced by specialized laryngeal vocal membranes on top of vocal folds. However, their function in vocal production remains untested. By filming vocal membranes in excised bat larynges (Myotis daubentonii) in vitro with ultra-high-speed video (up to 250,000 fps) and using deep learning networks to extract their motion, we provide the first direct observations that vocal membranes exhibit flow-induced self-sustained vibrations to produce 10 to 95 kHz echolocation and social communication calls in bats. The vocal membranes achieve the highest fundamental frequencies (fo’s) of any mammal, but their vocal range is with 3 to 4 octaves comparable to most mammals. We evaluate the currently outstanding hypotheses for vocal membrane function and propose that most laryngeal adaptations in echolocating bats result from selection for producing high-frequency, rapid echolocation calls to catch fast-moving prey. Furthermore, we show that bats extend their lower vocal range by recruiting their ventricular folds—as in death metal growls—that vibrate at distinctly lower frequencies of 1 to 5 kHz for producing agonistic social calls. The different selection pressures for echolocation and social communication facilitated the evolution of separate laryngeal structures that together vastly expanded the vocal range in bats.
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Римаренко, Євген Олександрович. "СУЧАСНИЙ СТАН ПРОБЛЕМИ РОЗРОБКИ ЗВУКОПОГЛИНАЮЧИХ КОНСТРУКЦІЙ ДЛЯ ГАЗОТУРБІННИХ ДВИГУНІВ." Aerospace technic and technology, no. 8 (August 31, 2020): 111–20. http://dx.doi.org/10.32620/aktt.2020.8.15.
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A review of current international aviation noise requirements is provided. It is shown that international requirements for aircraft noise levels are constantly increasing. The rapid growth of the international fleet leads to an increase in the number of take-offs and landings of aircraft at airports, and as a result, the problem of aircraft noise still relevant. To reduce noise levels at airports, various methods are used, one of which is the operational limitations of aircraft concerning the levels of noise they create. In European Union countries there are operational restrictions for aircraft meeting the requirements of Chapter 3 with a noise margin of less than 10 EPNdB. For already established aircraft that have passed certification, again it is necessary to look for methods to reduce noise. The main type of aircraft in operation in the world is an aircraft with turbofan engines. For such an aircraft, the main sources of noise during take-off will be the noise of the fan and jet, while landing, the noise of the landing gear, flaps, slats, and fan noise. When choosing a method of reducing aircraft noise, it should determine the source that most affects the overall noise level. It has been determined that fan noise is one of the main sources of noise. Acoustic liners constructions are widely used to reduce the noise level created by the fan. They are one of the most priority areas for reducing fan noise. Achievements in the use of acoustic liners to decrease the noise of domestic aircraft An-124-100, An-148-100 are considered. It is noted that due to the increasing requirements for aircraft noise, it is necessary to use new acoustic liners with improved sound-absorbing properties. It was determined that it is possible to improve the sound-absorbing properties of the acoustic liners by expanding the frequency range of sound absorption of such structures.Modern methods for improving the acoustic properties of the acoustic liners are presented: the use of multilayer resonant acoustic liners makes it possible to customize the design for an increased number of calculation parameters; the use of modified variants of the acoustic liners core such as corrugated core, oversized perforated core; the use of porous and porous fiber materials in the design of the acoustic liners to provide additional sound-absorbing ability, the use of low-frequency acoustic liners to reduce the noise of promising turbofan engines with a high and ultra-high bypass ratio.
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Amal Sudaraka Samarasinghe, Haththotuwa Gamage, Sandarenu Dharmaprema, Udani Manodya, Kalmee Pramoda Kariyawasam, and Udara Chandrajith Samaranayake. "Exploring Impact of the Ultrasound and Combined Treatments on Food Quality: A Comprehensive Review." Turkish Journal of Agriculture - Food Science and Technology 12, no. 2 (February 27, 2024): 349–65. http://dx.doi.org/10.24925/turjaf.v12i2.349-365.6478.
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As a response to the evolving consumer demand for healthier food choices, ultrasound application in food processing emerges as a sustainable and green solution with no residual effects. This method, known for its cost-efficiency and sustainability, holds significant promise in meeting the increasing need for high-quality, chemical-free, and natural-tasting convenience foods in the ever-changing landscape of the food industry. Ultrasound, leveraging mechanical sound waves, spans across various frequencies: power ultrasound (20–100 kHz), high-frequency ultrasound (100 kHz-1 MHz), and diagnostic ultrasound (1–500 MHz). This study focuses on investigating the impact of ultrasound and combined treatments on food quality, summarizing their diverse applications across different unit operations such as texture and rheology, emulsification and homogenization, crystal formation and modification, dehydration and drying, fermentation, filtration, preservation and shelf-life extension, flavor enhancement, color and appearance, antioxidant activity, enzyme activity and food digestibility, bioavailability and bio-accessibility, and specific food divisions including unprocessed, minimally processed, processed, and ultra-processed foods, as well as culinary ingredients. It delves into their effects on technological and functional aspects of food products, explores emerging trends, offers possible recommendations in ultrasound technology for the food industry, while also recognizing existing challenges and limitations associated with ultrasound and related technologies.
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Dong, Liang, Yuqi Zhao, and Cui Dai. "Detection of Inception Cavitation in Centrifugal Pump by Fluid-Borne Noise Diagnostic." Shock and Vibration 2019 (March 26, 2019): 1–15. http://dx.doi.org/10.1155/2019/9641478.
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This paper presents an experimental methodology that is capable of sensitively detecting the cavitation inception in a centrifugal pump. Firstly, with a centrifugal pump of ns=117 as research object, the cavitation performance, the bubble pattern distribution at impeller inlet, and the vibration and noise were synchronously measured at different flow conditions each with several cavitation coefficients. The change laws of total level of vibration and noise signals throughout the cavitation process were emphatically investigated. After comparing the sensitivity and reliability of different detection methods, the method based on overall sound pressure level of liquid-borne noise is found to present high sensitivity to cavitation. Secondly, by comparing the affected 1/3 octave spectrum by changing flow and cavitation coefficients, the highly sensitive frequency band to cavitation was obtained. Then, a new inception cavitation detection method was proposed based on Pauta principle. Finally, the method was verified through an ultra-low-specific speed pump (ns=25). The results show that the total pressure level of liquid-borne noise increases firstly and then decreases with the development of cavitation. The broadband SPL of liquid-borne noise between 2000 and 3000 Hz can be used to detect the inception cavitation, and the cavitation detection threshold is determined as 1.0%.
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Gao, Xu, Jiajie Wen, Jiajia Wang, and Kaiwei Li. "Broadband Acoustic Sensing with Optical Nanofiber Couplers Working at the Dispersion Turning Point." Sensors 22, no. 13 (June 30, 2022): 4940. http://dx.doi.org/10.3390/s22134940.
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Herein, a broadband ultrasensitive acoustic sensor based on an optical nanofiber coupler (ONC) attached to a diaphragm is designed and experimentally demonstrated. The ONC is sensitive to axial strain and works as the core transducing element to monitor the deformation of the diaphragm driven by acoustic waves. We first theoretically studied the sensing property of the ONC to axial strain and the deformation of the diaphragm. The results reveal that ONC working at the dispersion turning point (DTP) shows improved ultra-sensitivity towards axial strain, and the largest deformation of the circular diaphragm occurs at the center. Guided by the theoretical results, we fabricated an ONC with a DPT at 1550 nm, and we fixed one end of the ONC to the center of the diaphragm and the other end to the edge to construct the acoustic sensor. Finally, the experimental results show that the sensor can achieve accurate measurement in the broadband acoustic wave range of 30~20,000 Hz with good linearity. Specifically, when the input acoustic wave frequency is 120 Hz, the sensitivity reaches 1923 mV/Pa, the signal-to-noise ratio is 42.45 dB, and the minimum detectable sound pressure is 330 μPa/Hz1/2. The sensor has the merits of simple structure, low cost, and high performance, and it provides a new method for acoustic wave detection.
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Jesrani, Ameet, Pari Gul, Nida Khan, Seema Nayab, and Fahmida Naheed. "Ultrasound Employed to Detect Breast Lumps among Symptomatic Patients in Tertiary Care Hospital." Journal of Bahria University Medical and Dental College 10, no. 4 (October 1, 2020): 296–300. http://dx.doi.org/10.51985/jbumdc2020032.
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Objective: To assess different pathological breast lesions in ultra sound in a subgroup of population. Study design and setting: It was a cross sectional study conducted at Bolan Medical Complex Hospital Quetta, Pakistan from June 2018 to January 2019. Methodology: Total 103 patients with breast swelling, pain and discharge were targeted. Gray scale and Doppler Ultrasound of breast followed by FNAC/biopsy of breast lesion was performed. Data presented as mean ± standard deviation for continuous variables and frequency with percentages for categorical variables. Results: Out of 48 clinically palpable lumps US detected all of 48 lumps and additionally 12 clinically non palpable masses were detected on US examination. Thus, overall sensitivity of ultrasound in detecting breast lumps was 100%. Fibroadenoma of the breast was diagnosed accurately in 80.3% of women. Ultrasound reliably differentiated cystic from solid breast masses (100%). The sensitivity of ultrasound for detecting breast carcinoma was 63.4% with a positive predictive value of 87.5%, a negative predictive value of 99.5% and accuracy of 58.33%. US findings most suggestive of benign lesions were oval or round shape in 88.3%, well defined margin in 84%, absent lobulation in 86.04% and wider than taller ratio in 90.69% of the cases.US findings of most predictive for malignancy were of irregular shape in 81.8%, ill-defined margin in 90.9% and length to height ratio in 63.6% of cases. Conclusion: Ultrasound is simple, cheap, safe and relatively accessible imaging modality for evaluation of breast pathologies. Due to its high sensitivity in diagnosing benign breast lesions particularly cystic lesions and fibroadenoma unnecessary interventions can be avoided
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Fesenko, Marina A., Galina V. Golovaneva, Tatyna Yu Miteleva, and Peter A. Vuicik. "The influence of harmful occupational physical factors on the male workers’ reproductive health (analytical review)." Russian Journal of Occupational Health and Industrial Ecology 63, no. 8 (September 5, 2023): 528–36. http://dx.doi.org/10.31089/1026-9428-2023-63-8-528-536.
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This paper provides a review of the literature for the analysis and assessment of the occupational risk of reproductive health disorders of male workers under the influence of harmful physical factors of production.
To assess the risk of exposure to harmful industrial physical factors on the reproductive health of male workers, the authors have applied the method of analytical review of the data obtained.
Literature data show that the work of men in conditions of both high and low temperatures can lead to a violation of reproductive function. In the bakery, ceramic, steel, welding and other industries, working conditions are characterized by the presence of hyperthermia. Researchers have identified a violation of reproductive function in male workers, along with changes in the physiological parameters of the body's homeostasis.
There are few studies on the effects of noise and vibration on the reproductive health of working men, and there are few studies on the effects of ultra- and infrasound. The consequences of such exposure are disorders of hormonal status, spermatogenesis, leading to further changes in reproductive function, impotence and infertility. Scientists confirm these data with experimental studies on animals and volunteers.
Exposure to ionizing radiation is a proven factor of reproductive dysfunction, which leads to changes in the quantity and quality of sperm, reproductive hormones. The consequence of exposure to ionizing radiation are chromosomal abnormalities, leading to congenital anomalies in offspring.
It has been shown that the biological effect of electromagnetic fields of various frequency ranges (cell phones, microwave ovens, laptops, devices with Wi-Fi, as well as other types of non–ionizing radiation — low-frequency electromagnetic fields and extremely high-frequency) on reproductive organs can manifest itself in changes in spermatogenesis indicators, DNA damage, genomic instability, hormonal regulation and work disorders protein kinases, hormones, antioxidant enzymes, leading to disorders of sexual behavior, decreased fertility, up to infertility.
The presented data show that harmful occupational physical factors can lead to violations of the reproductive health of male workers. Currently, there is no systematic approach to solving the problem. In this regard, it is necessary to develop a scientifically sound system for assessing occupational risk and making managerial decisions to preserve reproductive health, since a decrease in the fertility of male workers potentially affects the well-being of the family and society as a whole.
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Le, Thi H., An H. T. Phan, Khoa C. M. Le, Thy D. U. Phan, and Khoi T. Nguyen. "Utilizing polymer-conjugate albumin-based ultrafine gas bubbles in combination with ultra-high frequency radiations in drug transportation and delivery." RSC Advances 11, no. 55 (2021): 34440–48. http://dx.doi.org/10.1039/d1ra04983f.
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Ultrafine bubbles stabilized by human serum albumin conjugate polyethylene glycol ameliorates the stability of complex as well as the drug payload. Polyethylene glycol presents the crucial role in releasing drug by means of acoustic sound.
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Venyo, Anthony Kodzo-Grey. "Prostatic Abscess: A Review and Update." Archives of Medical Case Reports and Case Study 4, no. 6 (November 8, 2021): 01–22. http://dx.doi.org/10.31579/2692-9392/090.
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Prostate abscess (PA) is a complication that ensues an acute infectious purulent process within the prostate gland which is typified by accumulation of purulent material within the prostate gland and this purulent material could be unilocular or multi-septated within the prostate gland. PA is a rare disease especially in the developed world where PA tends to be more commonly associated with patients who have diabetes mellitus, chronic kidney disease, chronic liver disease, immunosuppressive disease, HIV Infection, renal transplantation, and long-term urethral catheterisation. PA tends to be more commonly encountered in the developing world. PA could be an acute abscess or chronic abscess especially in association with chronic inflammatory conditions including tuberculosis or intravesical instillations of Bacillus Calmette Guerin (BCG). PA tends to constitute 0.5% of all urology disease and 6% of all acute cases of bacterial prostatitis. The mortality rate associated with PA has tended to be between 1% and 16% of all cases of prostate abscess. PA tends to be most commonly encountered in individuals who are in their fifth to sixth decade and could occur at any age. PAs that are due to sexually transmitted organisms tend to be more commonly encountered in younger males. PA tends to affect the central zone as well as the peripheral zones of the prostate gland. Haematogenous dissemination from a primary source of infection from a primary infection elsewhere have been reported and some of the reported sources included respiratory tract, digestive tract, urinary tracts, skin, and soft tissue are very rare. PA has also been reported to be associated with staghorn calculus. Some of the reported bacterial organisms that have caused acute prostate abscess (APA) include: Escherichia Coli, Klebsiella, Pseudomonas, Proteus, Enterobacter, Enterococcus, and staphylococcus. Other causes of prostate abscess have included other bacteria and fungal infection including: Brucellosis, Salmonella, Nocardia, Mycobacterium tuberculosis. Prostate abscess has also been reported in association with malignancy of the prostate gland. Manifestations of prostate abscess could include: (a) systemic symptoms including pyrexia, chills, headache, general malaise, low back ache and in some rare cases of prostate abscess, a history of treatment for tuberculosis or contact with a person who has tuberculosis, or travel to a salmonella endemic area may be obtained and in cases of Brucellosis PAs drinking of raw milk / contact with animals may be elicited and or rare occasions treatment of superficial urothelial carcinoma with Bacillus Calmette Guerin may be elicited. (b) perineal pain, dysuria, urinary frequency, urinary urgency, retention of urine, recent prostate biopsy, visible haematuria, urethral discharge of pus, lower urinary tract obstructive symptoms with poor flow, intermittent flow, hesitancy, and sensation of incomplete emptying of the urinary bladder, retention of urine, and tenderness over the prostate gland with a feeling of bogginess and soft fluctuation. The symptoms tend to be non-specific. Diagnosis of PAs tends to be established based upon a good clinical history taking, good clinical examination, urinalysis and urine culture, routine haematology and biochemistry blood tests with evidence of raised white blood cell count and CRP and at times lymphocytosis in cases of tuberculous prostate abscess, blood culture, urine culture, PCR detection of sexually transmitted organisms, radiology imaging including trans-rectal ultra-sound scan of the prostate, or CT) scan of abdomen and pelvis including the prostate, or MRI scan of the prostate. Treatment of PA depending upon the size of the abscess has been undertaken with various options including: Appropriate antibiotic treatment alone for small abscesses based upon the antibiotic sensitivity pattern of the cultured organism, Antibiotic treatment and radiology image-guided aspiration of the abscess. Antibiotic treatment plus radiology image-guided insertion of a drain into the prostate abscess, trans-urethral incision / resection / modified resection of the prostate gland to deroof and drain the abscess, open drainage of the abscess is only undertaken on rare occasions. Within remote district hospitals in developing countries in the absence of radiology imaging, the clinician would have no choice but to undertake finger guided aspiration / drainage of the prostate abscess plus antibiotic treatment. It is important to obtain the culture and sensitivity result of the aspirated and drained pus so that if there are fungi cultured or rare organisms cultured the choice of antibacterial / antifungal treatment would depend upon the microbiology results. It is important to treat all complications urgently and appropriately including provision of intensive care. Careful clinical follow-up, laboratory investigations and radiology imaging are necessitated to ensure good recovery and to quickly identify as well as appropriately treat any recurrent abscess and on rare occasions if there is an associated prostate cancer it would be detected. The prognosis associated with the treatment of PA depends upon a number of factors including: Timely diagnosis and adequate and appropriate treatment of the PA. The underlying associated medical conditions of the patient. The prognosis tends to be good if the PA is diagnosed early as well as treated early including utilization of the correct anti-microbial medicament and appropriate drainage of the abscess. Poor prognosis tends to be associated with individual patients who are older than 65 years, fever with a temperature higher than 100.4 degrees Fahrenheit, benign prostatic hyperplasia, chronic long-term urethral catheterisation. In the scenario of non-availability of bacterial culture report in a remote area in a developing country when there is delay in getting the culture results from the regional or national centre there would be the possibility of utilizing a broad spectrum and potent antibiotics but if the organism is a fungus then there would tend to be recurrence of the abscess and poor outcome and for this reason it would be recommended that every hospital in the world should have access to good laboratory services including haematology, biochemistry, microbiology, pathology, and radiology services including ultrasound scan, computed tomography scan as well as magnetic resonance imaging scan as well as well trained staff to operative the various equipment as well as high dependency units and intensive care units and staff should be available to provide support for all patients that need support.
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Liang, Xiao, Haofeng Liang, Jiaming Chu, Zhen Yang, Zhuo Zhou, Nansha Gao, Siwen Zhang, Guojian Zhou, and Congfang Hu. "A composite acoustic black hole for ultra-low-frequency and ultra-broad-band sound wave control." Journal of Vibration and Control, August 10, 2023. http://dx.doi.org/10.1177/10775463231194702.
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Achieving ultra-low and ultra-broad-band sound absorption and full-band sound insulation is a major challenge. Here, we propose a composite structure of a multilayer micro-perforated plate and acoustic black holes to achieve this purpose. Combining the stable sound absorption effect of the multilayer micro-perforated plate in the full frequency band and the sound insulation effect of the acoustic black hole in the low frequency and the excellent sound absorption effect in the high frequency, the excellent sound control effect of 600–3150 Hz absorption coefficient greater than 0.8 and 100–3150 Hz sound transmission loss greater than 50 dB is achieved. The acoustic properties of different components and different acoustic black hole outlet were evaluated by finite element method, and the principles of sound absorption and insulation of the composite structure were elaborated. Finally, the results of finite element method are verified by impedance tube experiments. This work can make further progress in elucidating the acoustic properties of the ABH and open up new avenues in the control of ultra-low and ultra-wide frequency acoustic waves.
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Guan, Yi-jun, Yong Ge, Hong-xiang Sun, Shou-qi Yuan, Yun Lai, and Xiao-jun Liu. "Ultra-Thin Metasurface-Based Absorber of Low-Frequency Sound With Bandwidth Optimization." Frontiers in Materials 8 (September 30, 2021). http://dx.doi.org/10.3389/fmats.2021.764338.
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We report, both theoretically and experimentally, a type of ultra-thin metasurface-based low-frequency sound absorber with bandwidth optimization. Such a metasurface unit consists of an ultrathin resonator (thickness∼1/90 wavelength) with a circular hole on the upper panel and four narrow slits inside a multiple-cavity structure. Eigenmode simulations of the unit show rich artificial Mie resonances, in which a type of monopolar Mie resonance mode can be obtained at 238.4 Hz. Based on the excitation of the monopolar mode, we can realize the near-perfect low-frequency sound absorption with the maximum absorption coefficient and fractional bandwidth of 0.97 and 12.9%, respectively, which mainly arises from the high thermal-viscous loss around the circular hole and four narrow slits of the unit. More interestingly, by combining 4 units with different diameters of the circular hole, we further enhance the fractional bandwidth of the compound unit to 18.7%. Our work provides a route to design ultra-thin broadband sound absorbers by artificial Mie resonances, showing great potential in practical applications of low-frequency noise control and architectural acoustics.
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Peng, Xiuyuan, Junfei Li, and Steven A. Cummer. "Ultra-broadband low-frequency high-efficiency acoustic energy harvesting with metamaterial-enhanced loudspeakers." Applied Physics Letters 123, no. 7 (August 14, 2023). http://dx.doi.org/10.1063/5.0158079.
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Acoustic energy harvesters (AEHs) open up opportunities to recycle noise waste and generate electricity. They provide potential power solutions to a wide range of sensors. However, the practicality of AEHs has long been limited by their narrow bandwidths and low efficiencies. In this study, we present an ultra-broadband AEH and a highly efficient AEH that transforms sound energy into usable electrical power. Our broadband device comprises an electrodynamic loudspeaker driver and an optimized acoustic metamaterial matching layer and is capable of converting 7.6% to 15.1% of total incident sound energy from 50 to 228 Hz. Moreover, we demonstrate that by replacing the loudspeaker surround with a lower-loss material such as PDMS, the energy conversion rate can be significantly increased to 67%. The proposed broadband AEH has a fractional bandwidth eight times the state-of-the-art, while the proposed highly efficient AEH has a peak efficiency three times the state-of-the-art. The outstanding performance makes our designs cost-effective and scalable solutions for noise reduction and power generation.
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Cheng, Baozhu, Jiesen Zhang, Yang Liu, Jiaqi Sun, Bin Li, and Hong Hou. "Theoretical and experimental investigation on the sound absorption performance of ultra-thin curled acoustic metasurface." Journal of Low Frequency Noise, Vibration and Active Control, January 24, 2024. http://dx.doi.org/10.1177/14613484241228035.
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A simplified model of the absorption coefficient of traditional Helmholtz resonators (THR) was established, and the influence of different geometric parameters on the absorption coefficient of THR was analyzed. To realize the low-frequency broadband acoustic structure design, an accurate theoretical model for the sound absorption coefficient of the curled acoustic metasurface (CAM) unit was established. Based on the complex frequency plane method (CFPM), the CAM units with perfect sound absorption at four discrete frequencies were designed. The low-frequency broadband acoustic metasurfaces in parallel under decoupled and coupled conditions were studied, and the thickness is only 12 mm. The high efficiency of sound absorption above 0.8 was achieved in the frequency range of 758 Hz–940 Hz. The experiment verifies the efficient sound absorption effect of the CAM unit and the broadband sound absorption effect under coupled conditions. The research in this paper has a certain potential applications for low-frequency broadband noise control technology.
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Sibiryakova, Olga V., Ilya A. Volodin, and Elena V. Volodina. "Polyphony of domestic dog whines and vocal cues to body size." Current Zoology, August 13, 2020. http://dx.doi.org/10.1093/cz/zoaa042.
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Abstract In domestic dogs Canis familiaris, vocal traits have been investigated for barks and growls, and the relationship between individual body size and vocal traits investigated for growls, with less corresponding information for whines. In this study, we examined the frequency and temporal traits of whines of 20 adult companion dogs (9 males, 11 females), ranging in body mass from 3.5 to 70.0 kg and belonging to 16 breeds. Dog whines (26–71 per individual, 824 in total) were recorded in conditioned begging contexts modeled by dog owners. Whines had 3 independent fundamental frequencies: the low, the high and the ultra-high that occurred singly as monophonic calls or simultaneously as 2-voice biphonic or 3-voice polyphonic calls. From the smallest to largest dog, the upper frequency limit varied from 0.24 to 2.13 kHz for the low fundamental frequency, from 2.95 to 10.46 kHz for the high fundamental frequency and from 9.99 to 23.26 kHz for the ultra-high fundamental frequency. Within individuals, the low fundamental frequency was lower in monophonic than in biphonic whines, whereas the high fundamental frequency did not differ between those whine types. All frequency variables of the low, high, and ultra-high fundamental frequencies correlated negatively with dog body mass. For duration, no correlation with body mass was found. We discuss potential production mechanisms and sound sources for each fundamental frequency; point to the acoustic similarity between high-frequency dog whines and rodent ultrasonic calls and hypothesize that ultra-high fundamental frequencies function to allow private, “tete-a-tete” communication between members of social groups.
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Boccaccio, Marco, Konstantinos Myronidis, Michael Thielke, Michele Meo, and Fulvio Pinto. "A multifunctional ultra-thin acoustic membrane with self-healing properties for adaptive low-frequency noise control." Scientific Reports 12, no. 1 (October 22, 2022). http://dx.doi.org/10.1038/s41598-022-22441-4.
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AbstractThis paper proposes a novel multifunctional ultra-thin membrane based on a Polyborosiloxane-based gel with stimuli-responsive sound absorption and sound transmission loss (STL) and characterised by excellent self-healing properties. This adaptive behaviour is the result of a dynamically activated phase transition in the membrane’s polymeric network which is given by the interaction with the travelling sound pressure wave. The presence and the extent of such phase transition in the material was investigated via oscillatory rheological measurements showing the possibility to control the dynamic response by modifying the Boron content within the polymer. Acoustic analyses conducted at different stimuli responses showed high and dynamic absorption (95%) at the absorption coefficient peaks and an adaptive shift to lower frequencies while sound amplitudes were increased. An average STL up to 27 dB in the frequency range between 500 to 1000 Hz was observed and an increased STL above 2 dB was measured as the excitation amplitude was increased. Results demonstrated that the new membrane can be used to develop deep subwavelength absorbers with unique properties (1/54 wavelength in absorption and 1/618 in STL) able to tune their performance in response to an external stimulus while autonomously regaining their properties in case of damage thanks to their self-healing ability.
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Zhang, Xu, Hao Jing, Qing Zhang, Ruijun Zhang, and Lixin Liu. "Flow behavior and aerodynamic noise characteristics of ultra-high-speed elevator based on large eddy simulation." Engineering Computations, May 24, 2023. http://dx.doi.org/10.1108/ec-12-2021-0736.
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PurposeThis paper aims to guide the implementation of noise reduction measures in hoistway and reduce the aerodynamic noise generated by elevator operation, this paper aims to propose an aerodynamic noise analysis method that can solve the flow field in hoistway.Design/methodology/approachA turbulence-acoustic model solving the flow field in a hoistway and a numerical wind hoistway model of the ultra-high-speed elevator were established by using large eddy simulation (LES) and Curle acoustic theory.FindingsThe characteristics of pulsating flow field and aerodynamic noise around ultra-high-speed elevator are analyzed. The asymmetric characteristics of the flow field could be observed using the turbulent kinetic energy and the instantaneous vortexes in the wind hoistway model. Vortex shedding, air flow separation and recombination around the car were the key factors for aerodynamic noise generation. The sound pressure level was approximately linear to the logarithm of car speed. The increase of car deflection angle in a certain range would reduce the peak frequency of wake noise and increase the sound pressure level (SPL) value.Originality/valueThis paper provides important guidance for researches studying the aerodynamic noise in the hoistway and the technical personnel that look for the reduction measures, which greatly improves the shortcomings in the numerical simulation of the aerodynamic noise of the hoistway.
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Lage-Castellanos, Agustin, Federico De Martino, Geoffrey M. Ghose, Omer Faruk Gulban, and Michelle Moerel. "Selective attention sharpens population receptive fields in human auditory cortex." Cerebral Cortex, November 6, 2022. http://dx.doi.org/10.1093/cercor/bhac427.
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Abstract Selective attention enables the preferential processing of relevant stimulus aspects. Invasive animal studies have shown that attending a sound feature rapidly modifies neuronal tuning throughout the auditory cortex. Human neuroimaging studies have reported enhanced auditory cortical responses with selective attention. To date, it remains unclear how the results obtained with functional magnetic resonance imaging (fMRI) in humans relate to the electrophysiological findings in animal models. Here we aim to narrow the gap between animal and human research by combining a selective attention task similar in design to those used in animal electrophysiology with high spatial resolution ultra-high field fMRI at 7 Tesla. Specifically, human participants perform a detection task, whereas the probability of target occurrence varies with sound frequency. Contrary to previous fMRI studies, we show that selective attention resulted in population receptive field sharpening, and consequently reduced responses, at the attended sound frequencies. The difference between our results to those of previous fMRI studies supports the notion that the influence of selective attention on auditory cortex is diverse and may depend on context, stimulus, and task.
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Mathis, Gebhard, Rudolf Horn, Susanne Morf, Helmut Prosch, Serena Rovida, Gino Soldati, Beatrice Hoffmann, Michael Blaivas, and Christoph F. Dietrich. "WFUMB position paper on reverberation artefacts in lung ultrasound: B-lines or comet-tails?" Medical Ultrasonography, December 12, 2020. http://dx.doi.org/10.11152/mu-2944.
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The analysis of vertical reverberation artefacts is an essential component of the differential diagnosis in pulmonary ultra-sound. Traditionally, they are often, but not exclusively, called B-line artefacts (BLA) and/or comet tail artefacts (CTA), but this view is misleading. In this position paper we clarify the terminology and relation of the two lung reverberation artefacts BLA and CTA to spe-cific clinical scenarios. BLA are defined by a normal pleura line and are a typical hallmark of cardiogenic pulmonary edema after exclusion of certain pathologies including pneumonia or lung contusion, whereas CTAs show an irregular pleura line representing a variety of parenchymal lung diseases. The dual approach using low frequency transducers to determine BLA and high frequency transducer to determine the pleural surface is recommended.
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Parmar, Bhavisha, Mwanaisha Phiri, Louis Jailos, Regina Kachapila, Benjamin Saleb, Wakisa Mulwafu, Vinay Manchaiah, and M. Saad Bhamla. "Comparing outcomes of ultra-low-cost hearing aids to programmable, refurbished hearing aids for adults with high frequency hearing loss in Malawi: a feasibility study." Frontiers in Rehabilitation Sciences 4 (June 12, 2023). http://dx.doi.org/10.3389/fresc.2023.1153056.
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IntroductionAccess to ear and hearing health services are limited or non-existent in low-income countries, with less than 10% of the global production of hearing aids distributed to this population. The aim of this feasibility study was to compare the outcomes of an ultra-low-cost hearing aid (LoCHAid) to programmable, refurbished hearing aids for adults with high-frequency hearing loss, in Blantyre, Malawi.MethodsSixteen adults with high frequency hearing loss, and no prior experience of hearing aids, took part in this study, nine were fitted with the LoCHAid and seven were fitted with refurbished, programmable hearing aids, for a one-month trial. Five standardized hearing qualities questionnaires were used to compare outcomes pre and post device fitting and between devices. Questionnaire scales were analysed using general linear models and inductive thematic analysis was used to evaluate qualitative data.ResultsOverall, there was no significant difference found between LoCHAid and refurbished hearing aids, and the two device types each showed a similar degree of improvement after fitting. Qualitative data analysis identified two key themes: Sound Quality and User experience.ConclusionThe results from this feasibility study are encouraging, but a comprehensive, larger clinical study is needed to draw firm conclusions about the LoCHAid's performance. This study has identified key improvement indicators required to enhance sound quality and user experience of the LoCHAid.
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Okamoto, Yuki, Thanh-Vinh Nguyen, Hidetoshi Takahashi, Yusuke Takei, Hironao Okada, and Masaaki Ichiki. "Highly sensitive low-frequency-detectable acoustic sensor using a piezoresistive cantilever for health monitoring applications." Scientific Reports 13, no. 1 (April 20, 2023). http://dx.doi.org/10.1038/s41598-023-33568-3.
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AbstractThis study investigates a cantilever-based pressure sensor that can achieve a resolution of approximately 0.2 mPa, over the frequency range of 0.1–250 Hz. A piezoresistive cantilever with ultra-high acoustic compliance is used as the sensing element in the proposed pressure sensor. We achieved a cantilever with a sensitivity of approximately 40 times higher than that of the previous cantilever device by realizing an ultrathin (340 nm thick) structure with large pads and narrow hinges. Based on the measurement results, the proposed pressure sensor can measure acoustic signals with frequencies as low as 0.1 Hz. The proposed pressure sensor can be used to measure low-frequency pressure and sound, which is crucial for various applications, including photoacoustic-based gas/chemical sensing and monitoring of physiological parameters and natural disasters. We demonstrate the measurement of heart sounds with a high SNR of 58 dB. We believe the proposed microphone will be used in various applications, such as wearable health monitoring, monitoring of natural disasters, and realization of high-resolution photoacoustic-based gas sensors. We successfully measured the first (S1) and second (S2) cardiac sounds with frequencies of 7–100 Hz and 20–45 Hz, respectively.
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Ketten, Darlene R., James A. Simmons, Hiroshi Riquimaroux, and Andrea Megela Simmons. "Functional Analyses of Peripheral Auditory System Adaptations for Echolocation in Air vs. Water." Frontiers in Ecology and Evolution 9 (September 6, 2021). http://dx.doi.org/10.3389/fevo.2021.661216.
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The similarity of acoustic tasks performed by odontocete (toothed whale) and microchiropteran (insectivorous bat) biosonar suggests they may have common ultrasonic signal reception and processing mechanisms. However, there are also significant media and prey dependent differences, notably speed of sound and wavelengths in air vs. water, that may be reflected in adaptations in their auditory systems and peak spectra of out-going signals for similarly sized prey. We examined the anatomy of the peripheral auditory system of two species of FM bat (big brown bat Eptesicus fuscus; Japanese house bat Pipistrellus abramus) and two toothed whales (harbor porpoise Phocoena phocoena; bottlenose dolphin Tursiops truncatus) using ultra high resolution (11–100 micron) isotropic voxel computed tomography (helical and microCT). Significant differences were found for oval and round window location, cochlear length, basilar membrane gradients, neural distributions, cochlear spiral morphometry and curvature, and basilar membrane suspension distributions. Length correlates with body mass, not hearing ranges. High and low frequency hearing range cut-offs correlate with basilar membrane thickness/width ratios and the cochlear radius of curvature. These features are predictive of high and low frequency hearing limits in all ears examined. The ears of the harbor porpoise, the highest frequency echolocator in the study, had significantly greater stiffness, higher basal basilar membrane ratios, and bilateral bony support for 60% of the basilar membrane length. The porpoise’s basilar membrane includes a “foveal” region with “stretched” frequency representation and relatively constant membrane thickness/width ratio values similar to those reported for some bat species. Both species of bats and the harbor porpoise displayed unusual stapedial input locations and low ratios of cochlear radii, specializations that may enhance higher ultrasonic frequency signal resolution and deter low frequency cochlear propagation.
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Wu, Su, Hongcan Gu, Yandong Pang, Wen Liu, Jiabei Wang, and Junbin Huang. "Ultrathin interferometric hydrophone towed line array based on uwFBG." AIP Advances 13, no. 11 (November 1, 2023). http://dx.doi.org/10.1063/5.0163694.
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In order to improve the suitability of the fiber hydrophone towing line array, we propose an interferometric hydrophone towed line array with a diameter of 1.7 mm. The line array is an integration of sensitization and package, embedding grating sensors in the composite materials of Kevlar and polyurethane in an additional pultrusion process. The theory and experiment indicate that polymer cladding of pultrusion is an effective way to improve phase sensitivity, increasing mechanical strength and decreasing cable diameter simultaneously. Then, a hydroacoustic detection system, with a quasi-distributed ultra-weak fiber Bragg grating towed line array, based on unbalanced interference is established and its phase sensitivities are tested experimentally. The result is measured by the vibration liquid column method and compared with a standard piezoelectric underwater acoustic detector. Over the frequency range of 200–2000 Hz, the system has a good amplitude–frequency response. We obtain an average phase sound pressure sensitivity of about −147.96 dB (re 1 rad/μPa) and a relative flatness response of 3 dB. The experimental results show that this system provides the possibility of an integrated hydrophone towed linear array with high adaptability and reliability.
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Kumar Meena, Mukesh, and Kuldeep Kumar Mendiratta. "EVALUATION OF HAND AND WRIST JOINTS USING ULTRASONOGRAPHY AND DOPPLER IN PATIENTS OF RHEUMATOID ARTHRITIS: COMPARISON WITH CONVENTIONAL RADIOGRAPHY AND CLINICAL CORRELATION." INTERNATIONAL JOURNAL OF SCIENTIFIC RESEARCH, November 1, 2022, 3–6. http://dx.doi.org/10.36106/ijsr/9803107.
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Background- Ultrasound (US) together with power Doppler (PD) are progressively being employed to assess joint involvement in rheumatoid arthritis (RA). High-resolution US permits direct assessment of intra-articular and periarticular inammatory activity and structural damage in inammatory arthritis. To analyze the quality of point-of-care hand and wrist ultra Objective- sound (US) examination in patients with established rheumatoid arthritis, it's comparison with standard radiography and clinical correlation. This prospective study was performed in 32 Methodspatients. Gray scale and power doppler ultrasonography of bilateral hand and wrist joint were performed employing a high-frequency linear transducer. Various ndings were recorded together with synovial hypertrophy, Power Doppler abnormality, soft tissue thickening, tendonitis, joint effusion, periosteal reaction, and erosions. Composite ultrasound scores and Disease Activity Score 28 were calculated and compared. ResultsUltrasound detected a lot of abnormalities within hand joints than the clinical examination. Synovial hypertrophy was detected altogether in 24 (75%) patients on gray scale ultrasound, active synovitis detected by using Doppler US in 20 patients (62.5%), effusion was detected in 10 patients (37.5 %), bone erosions (mostly in DIP and PIP joints) were detected in 20 patients (62.5%) and X-ray nding was detected in 8 patients (25%). There was a positive correlation of Power Doppler with synovial hypertrophy, bone erosions, Erythrocyte Sedimentation Rate and Disease Activity Score. Ultrasound could be a helpful reliable modality for the target assess Conclusion- ment of both soft tissue and erosive joint changes occurring in early stage in rheumatoid arthritis. Power doppler scores can be applied with bigger accuracy than clinical scores of synovitis in rheumatologic practice to enable therapeutic choices and to evaluate disease outcome and response to treatment.
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Han, Jieting, Yu Zhang, Shiyang Li, Weirong Hong, and Dazhuan Wu. "On the reduction of the noise in a low-pressure turbine cascade associated with the wavy leading edge." Physics of Fluids 35, no. 9 (September 1, 2023). http://dx.doi.org/10.1063/5.0165080.
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The low-pressure turbine (LPT) has become a potential noise source for future ultra-high by-pass ratio engines. In this paper, the feasibility and mechanism of wavy leading edge (WLE) noise control in the LPT cascade model are analyzed. The flow field and acoustic data are obtained with the large eddy simulation and Ffowcs Williams–Hawkings methods, which are validated using experimental data. The acoustic results are compared for different models; the maximum noise reduction can achieve 8.6 and 3.7 dBA in the frequency bands of FR#2 (315–4000 Hz) and FR#4 (6300–16 000 Hz), respectively; the noise reduction does not vary proportionally to the WLE parameter. The noise source is identified in the baseline model, and then the effect of WLE amplitude and wavelength on the noise source and its control on pressure fluctuations are evaluated. The pressure statistics demonstrate that WLE with a smaller wavelength and a larger amplitude can reduce the impingement of stator wakes on the leading edge of the rotor and stabilize the pressure fluctuation. To analyze the mechanism of WLEs on noise control, the pressure spectrum in terms of amplitude and coherence coefficient is utilized to explain the excellent noise performance of the WLE model in FR#2. The proposed similarity coefficient of coherence can quantify the destructive interference level and thus the coherence characteristics of the sound source. Generally, the noise reduction level can be predicted by the combination of the similarity coefficient and the amplitude spectrum of the pressure fluctuations for the WLE models.
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Reidenberg, Joy S. "Back to the Beach: Adaptations that Enabled Terrestrial Mammals to Return to the Water." FASEB Journal 31, S1 (April 2017). http://dx.doi.org/10.1096/fasebj.31.1_supplement.86.2.
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Modern aquatic mammals are extremely diverse. This includes classic marine mammals such as cetaceans (whales, including dolphins and porpoises) and sirenians (manatees, dugongs), but also many amphibious mammals that spend some time on land (e.g., seals, otters, hippos, polar bears). Aquatic mammals retain terrestrial‐based systems that have been vastly modified for existence in water, but this alone does not make them extreme. However, within this group are some notable extremists: the cetaceans. They have the strangest anatomical aquatic adaptations – the ones with the “‐est” adjectives – enabling the deepest dive, slowest pulse, longest apnea, shortest exhalation, largest nose, narrowest mandible, strongest suction, biggest hyoid, widest mouth, stretchiest gular region, hairiest moustache, loudest sound, lowest song, longest tooth, highest vocalization, fattiest ear, tiniest external auditory meatus, densest tympanic bulla, curliest tongue, smoothest skin, stiffest cervical vertebrae, bumpiest forelimb, heaviest testes, and fastest copulation. For example, the sperm whale can dive to the bottom of the ocean and hold its breath for nearly an hour. Its head that is nearly one‐third of its body length, and is comprised of an enormous nose modified for sound production. Its mandible may plow the sea floor, and the hyoid and tongue create suction to engulf prey. The blue whale is the biggest mammal that ever existed, and has the widest mouth for engulfing prey. It has the largest larynx capable of making the loudest and lowest vocalizations. The narwhal has an elongated tooth that is likely the basis for the legend of the unicorn's horn. The dolphin uses modified nostrils to generate ultra high frequency sounds for echolocation, and uses acoustic fats as pinnae to receive sounds. A whale calf can curl the tongue into a straw for channeling milk when nursing underwater. Whale skin is very smooth enabling hydrodynamic water flow, and compressed/fused cervical vertebrae eliminate friction from lateral head deviations. The elongated flippers of humpback whales have bumps on the leading edge that increase efficiency. The porpoise is the smallest whale but has the largest testes and longest penis that can be rapidly extruded for the quickest mating. These amazing anatomical aquatic adaptations make cetaceans one of the most extreme groups of animals on Earth.
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Eitutis, Susan T., Deborah A. Vickers, Karen Tebbutt, Tisa Thomas, Dan Jiang, Anel de Klerk, Jennifer Clemesha, Mark Chung, and Manohar L. Bance. "A Multicenter Comparison of 1-yr Functional Outcomes and Programming Differences Between the Advanced Bionics Mid-Scala and SlimJ Electrode Arrays." Otology & Neurotology, October 27, 2023. http://dx.doi.org/10.1097/mao.0000000000004048.
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Objective To determine if there is a difference in hearing outcomes or stimulation levels between Advanced Bionics straight and precurved arrays. Study design Retrospective chart review across three implant centers. Setting Tertiary centers for cochlear and auditory brainstem implantation. Patients One hundred fifteen pediatric and 205 adult cochlear implants (CIs) were reviewed. All patients were implanted under the National Institute for Health and Care Excellence 2009 guidelines with a HiRes Ultra SlimJ or Mid-Scala electrode array. Main outcome measures Hearing preservation after implantation, as well as CI-only listening scores for Bamford-Kowal-Bench sentences were compared 1 year after implantation. Stimulation levels for threshold and comfort levels were also compared 1 year after implantation. Results Hearing preservation was significantly better with the SlimJ compared with the Mid-Scala electrode array. Bamford-Kowal-Bench outcomes were not significantly different between the two arrays in any listening condition. Stimulation levels were not different between arrays but did vary across electrode contacts. At least one electrode was deactivated in 33% of implants but was more common for the SlimJ device. Conclusion Modern straight and precurved arrays from Advanced Bionics did not differ in hearing performance or current requirements. Although hearing preservation was possible with both devices, the SlimJ array would still be the preferred electrode in cases where hearing preservation was a priority. Unfortunately, the SlimJ device was also prone to poor sound perception on basal electrodes. Further investigation is needed to determine if deactivated electrodes are associated with electrode position/migration, and if programming changes are needed to optimize the use of these high-frequency channels.
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"COMPARATIVE ANALYSISOF THE PROPERTIES OF LTA TYPE ZEOLITE DEPENDING ON THE PRODUCTION METHOD: HYDROTHERMAL AND ULTRASONIC." ChemChemTech 65, no. 9 (2022): 90–96. http://dx.doi.org/10.6060/ivkkt.20226509.6633.
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The aim of the work was to establish the main parameters of the study of the use of ultra-sound at the stage of synthesis in search of the physicochemical properties of the LTA type zeolite with the hydrothermal method of production. A maincondition for the synthesis of this zeolite is the presence of precursors, namely aluminates and cubic sodium aluminosilicates. Metakaolin, solid sodium hydroxide and aluminum oxide are used as raw materials for the synthesis of zeolite. Ultrasonic treatment is carried out at a frequency of 22 kHz and a frequency of 8 μm at the end ofthe concentrator for 10 min. The industrial analogue was synthesized according to TU 2163-005-21742510-2004. In this work, ammonia is used as a probe to study the acid–base properties of zeo-lite structures. The choice of ammonia is due to the high degreeof bases, which makes it possible to determine not only strongly acidic centers, but also to combine centers that determine the size of molecules. Dynamic activity in terms of water parameters at breakthrough concentration is ob-served in the flow protocol. The particle size of zeolites is measured by scanning electron micros-copy. It was found that in the sample synthesized using ultrasound, the concentration of exchangeable sodium cations is 2.5 times higher than in the hydrothermal analogue and is 80 and 30 μg-eq/100g, respectively. The strength and number of acid sites of the synthesized zeolites were determined by the method of thermally programmed desorption of ammonia. For the synthesized LTA zeolite, its values are in the range of 0.06 1019 U/m2, for the industrial analogue it is lower by 5-10% and rarely 0.05 1019 U/m2. Using the data on the kinetics of ammonia desorption at various heating rates, the values of activation energy for ammonia desorption were calculated. The results lie in the range from 18.26 to 74.27 kJ/mol. The study of acid-base properties showed a more developed sur-face of the zeolite obtained by the ultrasonic method, which explains the greater acidity and acti-vation energy.
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Guzzardi, Giuseppe, Angelo Spinazzola, Gianluca Cangiano, Massimiliano Natrella, Andrea Paladini, Carla Porta, Luca Boccalon, et al. "Endovascular treatment of femoro-popliteal disease with the Supera stent: results of a multicenter study." Journal of Public Health Research, September 30, 2021. http://dx.doi.org/10.4081/jphr.2021.2360.
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Background: Even though many types of stents have been tested in superficial femoral artery (SFA) and popliteal artery (PA), the vast majority of these devices have provided an unsatisfactory outcome, probably due their unsuitable anatomical and physiological characteristics. The Supera peripheral stent (Abbott Vascular, Santa Rosa, CA, USA) is a braided interwoven nitinol device specifically designed for treating atherosclerotic lesions of the femoro-popliteal segment. The aim of this multicenter retrospective study was to describe the effectiveness of Supera stents in the management of femoral-popliteal atherosclerotic lesions and to critically analyze our findings in the context of current and past literature.Design and Methods: In this study we enrolled only patients who satisfied the inclusion criteria: 1) patients affected by chronic obstructive arterial disease (COAD) grade II, as per Rutherford classification; 2) patients treated with endovascular revascularization and Supera stent implantation in the femoro-popliteal axis. We retrospectively analyzed the Doppler Ultra-sound (US) follow-up at 12-24 and 36 month in order to detect the vascular occlusions. The primary patency, primary patency assisted and TLR were described statistically analyzed by survival analysis and the demographic data, clinical data, device safety following stenting were described as frequency and mean value.Results: 105 endovascular procedures on 99 patients for femoro-popliteal stenting with Supera were performed in four Italian hospitals. The median follow-up was 39 months (range 6-72), with primary patency rate of 83.1%, 74.3% and 69.5% at 12, 24 and 36 months after the procedure. The primary patency assisted was 89.9%, 76.8% and 73.4% in the same period, while the freedom from TLR values were 92.7%, 91.5% and 89.5% at 12, 24 and 36 months after the procedure, respectively. The mortality rate recorded at 12 months from the Supera implantation was 2.8% (3 out of 99 patients enrolled).Conclusions: Our data were in agreement with the current literature, showing the non-inferiority Supera stent in relation to the other stent available. Supera stent showed an excellent safety, effectiveness profile and high durability for the treatment of PAD patients with femoro-popliteal artery disease.
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Xiao, Tong, Xiaojun Qiu, and Benjamin Halkon. "Ultra-broadband local active noise control with remote acoustic sensing." Scientific Reports 10, no. 1 (November 27, 2020). http://dx.doi.org/10.1038/s41598-020-77614-w.
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AbstractOne enduring challenge for controlling high frequency sound in local active noise control (ANC) systems is to obtain the acoustic signal at the specific location to be controlled. In some applications such as in ANC headrest systems, it is not practical to install error microphones in a person’s ears to provide the user a quiet or optimally acoustically controlled environment. Many virtual error sensing approaches have been proposed to estimate the acoustic signal remotely with the current state-of-the-art method using an array of four microphones and a head tracking system to yield sound reduction up to 1 kHz for a single sound source. In the work reported in this paper, a novel approach of incorporating remote acoustic sensing using a laser Doppler vibrometer into an ANC headrest system is investigated. In this “virtual ANC headphone” system, a lightweight retro-reflective membrane pick-up is mounted in each synthetic ear of a head and torso simulator to determine the sound in the ear in real-time with minimal invasiveness. The membrane design and the effects of its location on the system performance are explored, the noise spectra in the ears without and with ANC for a variety of relevant primary sound fields are reported, and the performance of the system during head movements is demonstrated. The test results show that at least 10 dB sound attenuation can be realised in the ears over an extended frequency range (from 500 Hz to 6 kHz) under a complex sound field and for several common types of synthesised environmental noise, even in the presence of head motion.
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Dreye. Holt, M., A. K. Warzecha, N. S. Bülow, S. O. Skouby, A. L. M. Englund, K. Birc. Petersen, and N. S. Macklon. "P–613 Adjuvant letrozole in ovarian stimulation for in vitro fertilization does not reduce uterine peristalsis frequency prior to fresh embryo transfer." Human Reproduction 36, Supplement_1 (July 1, 2021). http://dx.doi.org/10.1093/humrep/deab130.612.
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Abstract Study question Does adjuvant letrozole in ovarian stimulation (OS) for in vitro fertilization (IVF) decrease the uterine peristalsis frequency (UPF) prior to fresh embryo transfer (ET)? Summary answer Adjuvant letrozole in (OS) for IVF does not reduce the UPF significantly prior to fresh ET. What is known already Throughout the cycle UPF aids spermatozoa transport to the fallopian tube and may affect implantation. At fresh, ET UPF is negatively correlated with implantation- and clinical pregnancy rates and is believed to be modulated by estradiol and progesterone. High levels of estradiol, from multiple follicular development, in OS have been reported to increase UPF, whereas progesterone is considered to be utero-relaxant. The influence of androgens is unclear. Co-treatment with letrozole during gonadotropin OS limits the estradiol rise the supra-physiological estradiol and may therefore reduce UPF prior to fresh ET. Study design, size, duration: This single centre study was nested within a multicentre double blinded RCT investigating the impact of letrozole co-treatment during gonadotropin OS for IVF on late follicular and luteal estradiol, progesterone and testosterone levels. Between 2016 and 2017, 39 women expected normal responders were randomised to co-treatment with letrozole or placebo. Of these, 33 women completed this element of the study. The study was carried out according to the Helsinki Declaration and the ICH-Good-Clinical-Practice. Participants/materials, setting, methods Eligible women were randomised 1:1 to adjuvant treatment with letrozole 5 mg/day or placebo in an antagonist protocol using a fixed dose of recFSH 150 IU/day. Final maturation was triggered with rhCG 6,500 IU and luteal support with vaginal progesterone was administered from the day following oocyte aspiration. Less than one hour prior to fresh ET, six minute duration transvaginal ultrasound recordings of the uterus in sagittal section were performed and blood samples were drawn. Main results and the role of chance A total of 33 women completed the study (letrozole n = 17; placebo n = 16). Age, BMI, and ovarian reserve markers were similar between the groups. On day of ET, serum estradiol levels were significantly suppressed in the letrozole group to mean 867 ± 827 pmol/L compared to 3,110 ± 1,528 pmol/L in the placebo group (P < 0.0001). Mean UPF prior to fresh ET did not differ between the intervention and control group (3.3 ± 0.36 versus 3.5 ± 0.51 per minute respectively, P = 0.108). UPF was assessed and agreed by two observers who were blind to adjuvant treatment. Two patients were excluded due to poor quality of the ultra sound recording. Supra-physiological serum estradiol in the placebo group was negatively correlated with UPF (P = 0.014; R = –0.62), but the more physiological serum estradiol levels in the letrozole group showed no correlation with UPF (P = 0.567; R = 0.15). Serum progesterone levels were similar in both groups and did not show any significant correlation with UPF. Testosterone levels were significantly higher in the letrozole group (P = 0.005) and showed a non-significant trend negatively correlated with UPF in the placebo group (P-value=0.07, R= –0.48). Limitations, reasons for caution The limited sample size risks masking minor effects. Wider implications of the findings: The supra-physiological levels of estradiol were significantly supressed in the intervention group, but UPF prior to fresh ET was similar in both groups. UPF is not strongly correlated to luteal phase sex steroid levels. Any beneficial effect of adjuvant letrozole during OS is not through an impact of UPF. Trial registration number NCT02939898