Relevant bibliographies by topics / Rotating Sound Sources

Academic literature on the topic 'Rotating Sound Sources'

Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Rotating Sound Sources"

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Yost, William, Xuan Zhong, and Anbar Najam. "Rotating sound sources and listeners: Sound source localization is a multisensory/cognitive process." Journal of the Acoustical Society of America 137, no. 4 (April 2015): 2200–2201. http://dx.doi.org/10.1121/1.4920001.

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Yost, William, and M. Torben Pastore. "Sound source localization in two-dimensions: Rotating sources and listeners." Journal of the Acoustical Society of America 145, no. 3 (March 2019): 1873. http://dx.doi.org/10.1121/1.5101771.

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Hansen, Niels Chr, and David Huron. "Twirling Triplets: The Qualia of Rotation and Musical Rhythm." Music & Science 2 (January 1, 2019): 205920431881224. http://dx.doi.org/10.1177/2059204318812243.

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While musicologists have long noted that triplet rhythms evoke sensations of rotation in listeners, no theory has been proposed to account for this apparent association. To investigate this phenomenon, 33 excerpts of “spinning, rotating, twirling, or swirling” music were crowd-sourced from an online discussion forum. Analysis revealed a prominence of fast, repeated, isochronous patterns using stepwise pitch movement, with significantly more compound meters than generally found in Western music. Inspired by ecological acoustics, an Ecological Theory of Rotating Sounds (ETRoS) is proposed to explain these associations. The theory maps patterns of loudness fluctuations to trajectories of rotating sound sources. Two experiments tested the theory. In Experiment A, listeners rated how much binary, ternary, quaternary, and quinary figures (of 2–5 notes) evoked sensations of rotation. Experiment B used a two-alternative forced-choice paradigm pitting ecological quaternary stimuli (strong-medium-weak-medium) against unecological stimuli with permuted stress values more typical of Western music (strong-weak-medium-weak). Results indicate that perceived rotation increases with tempo and is poorly evoked by binary rhythms. Loudness patterns consistent with rotating trajectories were perceived as more rotating than unecological patterns—but only when pitch was also moving. Altogether, moderate support is provided for an acoustic-ecological account of rotating sounds.
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Ocker, Christof, and Wolfram Pannert. "Three-dimensional acoustic energy flow from rotating sound sources." Acta Acustica 5 (2021): 48. http://dx.doi.org/10.1051/aacus/2021042.

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A detailed study of the three-dimensional sound fields around a monopole point source in subsonic and supersonic rotation is investigated. We calculate the sound pressure, the acoustic velocity, as well as the instantaneous and time-averaged acoustic intensity fields with the advanced time approach. The advanced time approach is applied for sound sources at subsonic and supersonic rotation and yield comparable results as those obtained from the spherical harmonic series expansion method or the solution of the retarded time equation. Further, the direction of the time-averaged acoustic energy flow is derived from the acoustic intensity vectors. It is shown, that the direction of the energy flow path differs from the radial direction and depends on the rotational direction and rotational velocity. Those findings are useful, for example, to improve the acoustic absorption performance of sound absorbers and acoustic liners around turbomachines.
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Xiao-Xia Guo, Xiao-Xia Guo, Rui-Qi Zhang Xiao-Xia Guo, Shu-Hao Liu Rui-Qi Zhang, Chen Wan Shu-Hao Liu, Zhen-Yu Wang Chen Wan, and Rong-Rong Han Zhen-Yu Wang. "Visualization of Rotating Machinery Noise Based on Near Field Acoustic Holography." 電腦學刊 33, no. 4 (August 2022): 215–23. http://dx.doi.org/10.53106/199115992022083304018.

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<p>In order to solve the problem of fast identification of the noise source of rotating machinery, the time-space complex envelope model of monopole sound source is studied, and a modulation method of the complex envelope is proposed. A method combining near-field acoustic holography technology and complex envelope information is proposed to reconstruct the sound field and realize the identification of rotating machinery noise sources. Using the overall fluctuation of the signal to identify the noise source of the rotating machinery greatly reduces the amount of calculation, and speeds up the positioning speed while ensuring the positioning accuracy. According to the sound field radiation characteristics of rotating machinery noise, different measurement distances, different sampling points numbers and different reconstruction distances are selected to reconstruct the sound field. The simulation data analysis results show that the near-field acoustic holography technology can still obtain high sound field reconstruction accuracy under the condition of large reconstruction distance, and does not require high sampling points numbers. Using the envelope information extracted by envelope modulation technology to reconstruct the sound field can accurately identify the number and geometric distribution of sound sources. This technology not only speeds up data processing, but also ensures the accuracy of sound field reconstruction.</p> <p>&nbsp;</p>
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Xu, Kunbo, Yun Shi, Weiyang Qiao, and Zhirong Wang. "The Methodological and Experimental Research on the Identification and Localization of Turbomachinery Rotating Sound Source." Energies 15, no. 22 (November 17, 2022): 8647. http://dx.doi.org/10.3390/en15228647.

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The localization and quantification of turbomachinery rotating sound sources is an important challenge in the field of aeroacoustics. In order to compensate the motion of a rotating sound source, a rotating beamforming technique is developed and applied in a flow duct, which uses a wall-mounted microphone array placed circularly parallel to the fan, to detect the broadband noise source of the aeroengine fan. A simulation of three discrete rotating sound sources with a non-constant rotational speed is pursued to verify the effectiveness in reconstruction of the correct source positions and quantitative prediction of the source amplitudes. The technique is ulteriorly experimentally implemented at an axial low-speed fan test rig facility. The fan test rig has 19 rotor blades and 18 stator vanes, with a design speed up to 3000 rpm. The method can accurately identify the radial and circumferential positions of the three rotating sound sources in the simulation case, large side-lobes appear near the main-lobe of the sound source due to the geometric influence of the microphone array. A noticeable feature of beamforming images for axial flow fan is that the sound sources appear to be concentrated in the tip region rather than distributed along the span.
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Carley, Michael. "Series expansion for the sound field of rotating sources." Journal of the Acoustical Society of America 120, no. 3 (September 2006): 1252–56. http://dx.doi.org/10.1121/1.2221410.

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Sales, G. D., K. J. Wilson, K. E. V. Spencer, and S. R. Milligan. "Environmental ultrasound in laboratories and animal houses: a possible cause for concern in the welfare and use of laboratory animals." Laboratory Animals 22, no. 4 (October 1, 1988): 369–75. http://dx.doi.org/10.1258/002367788780746188.

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Many laboratory animals are known to be sensitive to sounds (ultrasounds) beyond the nominal upper limit (20 kHz) of the human hearing range. Sources of sound in laboratories and animal houses were examined to determine the extent of ambient ultrasound. Of 39 sources monitored, 24 were found to emit ultrasonic sounds. Many of these (e.g. cage washers and hoses) also produced sound in the audible range. Running taps, squeaky chairs and rotating glass stoppers created particularly high sound pressure levels and contained frequencies to over 100 kHz. The oscilloscopes and visual display units investigated provided particular cause for concern as they emitted sounds that were entirely ultrasonic and therefore were apparently silent. Ambient ultrasound therefore appears to be common in laboratories and animal houses. It is suggested that its effect on laboratory animals should be investigated and guidelines on acceptable levels be formulated.
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Xue, W. F., J. Chen, J. Q. Li, and X. F. Liu. "Acoustical feature extraction of rotating machinery with combined wave superposition and blind source separation." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 220, no. 9 (September 1, 2006): 1423–31. http://dx.doi.org/10.1243/0954406jmes189.

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As the result of vibration emission in air, machine sound signal carries affluent information about the working condition of machine and it can be used to make mechanical fault diagnosis. The fundamental problems with fault diagnosis are the estimation of the number of sound sources and the localization of sound sources. The wave superposition can be employed to identify and locate sound sources, which is based on the idea that an acoustic radiator can be approximated and represented by the sum of the fields due to a finite number of interior point sources. But, in practice, a large number of measurements must be used in order to achieve a desired resolution, which makes the reconstruction process very time-consuming and expensive. In this paper, a combined wave superposition method has been developed reconstruct to acoustic radiation from machine acoustical signals. This method combines the advantages of both the wave superposition and Helmholtz equationleast squares methods, and it allows for reconstruction of the acoustic field from an arbitrary object with relatively few measurements, thus significantly enhancing the reconstruction efficiency. After sound source localization, the blind source separation (BSS) is proposed to extract acoustical feature from the mixed measuring sound signals. In a semi-anechoic chamber, a cross-planar microphone array, which consists of 29 microphones, was successfully applied to obtain the two-dimensional mapping of the sound sources. The location, the sound pressure, and the properties in frequency domain of the sound sources can be found through this method precisely. The experimental results demonstrate that the methods presented can potentially become an acoustical diagnosis tool.
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Tóth, Bence, János Vad, and Gábor Kotán. "Comparison of the Rotating Source Identifier and the Virtual Rotating Array Method." Periodica Polytechnica Mechanical Engineering 62, no. 4 (July 16, 2018): 261–68. http://dx.doi.org/10.3311/ppme.11194.

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The aim of this paper is to present two acoustic beamforming methods developed for rotating sources, namely the Rotating Source Identifier (ROSI) and the Virtual Rotating Array method (VRAM). These were applied onto a series of simulated test cases, and their behaviour was analysed. Both methods were able to localise the source reliably. However, the source strength was found to depend on the number or microphones when VRAM was applied. This phenomenon was quantified and an approximate formula was given providing the minimum number of microphones required to reach a certain amplitude error. Beamwidth and side lobe suppression were found to agree between the two methods, meaning that the way rotation is handled does not significantly affect the point spread functions. The computational cost of ROSI was two to three orders of magnitude higher than that of VRAM. The results show that both methods are applicable for the beamforming analysis of rotating sound sources. However, in case of VRAM, the number of microphones has to be chosen carefully to obtain reliable amplitude results.
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Dissertations / Theses on the topic "Rotating Sound Sources"

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Chih-Hao, Chen, and 陳志豪. "The Application of Sound Intensity for Noise Source Identification of Rotating Machinery." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/26000128382879124472.

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碩士
國防大學中正理工學院
造船工程研究所
89
The noise generated by the machinery which aboard on the Naval ships impacts the capability of anti-submarine　warfare. The effort to control　or prevent the noise from the machinery becomes an important study topic. Therefore, the study of the noise source identification is the first task in noise analysis. In this paper, we used the sound intensity measurements of a 45 KW DC motor to identify the noise source. The measurement results show that the main noise source of the 45KW DC motor is the cooling fan motor. The maximum sound power is located on the 1/3 octave band with 1000HZ center frequency. The results also indicate that there have good correlations between noise and vibration measurements.
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Hsu, Jui-Huang, and 徐瑞鍠. "Analysis of the vibration and corresponding sound field of the holed plate excited by a rotating sound source." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/68708631258316417850.

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碩士
國立中央大學
機械工程研究所
93
Abstract The purpose of this research is to apply the use of “Ectoplasm” for the vibration analysis and corresponding sound field analysis of the holed plate excited by a rotating sound source. This formulation allows predication of high order eigenfrequencies and mode shape of a simply supported plate with holes. Such an algorithm can avoid a non-unique problem with ill-conditioned mass and stiffness matrices. In this study, Hamilton’s principle is used to obtain the governing equations. Then, the dynamic responses due to rotating sound source are solved. The Kirchhoff-Helmholtz integral and the Green’s function are used to deal with the acoustic field of the holed plate. Radiation and diffraction of the system is discussed.
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Book chapters on the topic "Rotating Sound Sources"

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Maier, Christian, Wolfram Pannert, and Winfried Waidmann. "Localization of Rotating Sound Sources Using Time Domain Beamforming Code." In Advanced Structured Materials, 49–57. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-02836-1_4.

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Maier, Christian, Wolfram Pannert, and Winfried Waidmann. "Localization of Rotating Sound Sources Using Time Domain Beamforming Code." In Advanced Structured Materials, 161–68. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-00506-5_10.

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Maier, Christian, and Wolfram Pannert. "Implementation of Beamforming Codes in 3D CFD Simulations for the Localization and Visualization of Rotating Sound Sources." In Advanced Structured Materials, 201–14. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-20801-1_15.

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Zheng, Xie, Xunnian Wang, Jun Zhang, Kun Zhao, Zhengwu Chen, Yong Wang, and Ben Huang. "Recognition Location Method of Sound Source Based on Rotating Microphones." In Fluid-Structure-Sound Interactions and Control, 145–52. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-4960-5_23.

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Griffiths, Shelly. "Surgery." In Oxford Assess and Progress: Clinical Medicine. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198812968.003.0018.

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Starting a surgical job can feel like learning a completely new language. It may be the first time seeing patients in acute severe pain with a variety of lumps and bumps and a past history of previously unheard of complex operations. It can be easy to get hung up on whether the distended large bowel loop on the X- ray is a caecal or sigmoid volvulus or whether the strangulated hernia is femoral or inguinal. Ultimately, however, the most important point is that, as a junior doctor, it is being able to recognize that the patient is acutely unwell and may require an operation that will save lives. Ironically, a surgical rotation involves little time in the operating theatre— mostly, it will be spent dealing with problems during the peri-­operative period. This may start a week or two before the patient is even admitted, in the shape of a pre- assessment clinic, though these are increasingly nurse- led clinics with minimal input from junior doctors. Such clinics are, however, a good opportunity to see stable patients with interesting pathology and good clinical signs and to establish how well they look before the majority of their large bowel or their stomach is removed. The preoperative preparation of the patient goes beyond bloods and a cursory chat, and will require one to be on the lookout for previously undiagnosed cardiorespiratory or rheumatological conditions, among others, that might affect the patient getting to sleep or staying safely asleep under anaesthesia. Liaising with the anaesthetist about possible sources of difficulty well in advance of the planned procedure will ensure that operations do not get cancelled. The acute abdomen will take centre stage during general surgical takes. A thorough history and sound anatomical knowledge will help create a list of differential diagnoses. Accurate and careful palpation of the abdomen will reveal peritonism and the presence of any masses, and simple bedside observations and tests can greatly aid the diagnosis. Surgical specialties have a heavy reliance on imaging— erect chest X- ray, ultrasound, computed tomography (CT)/ magnetic resonance imaging (MRI) scan— each providing different information for the symp­toms displayed.
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Conference papers on the topic "Rotating Sound Sources"

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Haid, Daniel A., and Luc Mongeau. "Method for Measuring the Sound Intensity of Rotating Broadband Aerodynamic Noise Sources." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0086.

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Abstract A method was investigated for the measurement of the near field sound intensity of rotating broadband noise sources. The method used two sound intensity probes held stationary in the laboratory reference frame, which were conditionally sampled to track the motion of pre-defined rotating source regions along their circumferential path. The cross-correlation coefficient of the sound intensity for a single location in the rotating frame of reference was then calculated from the two stationary probe signals. Multiple probe spacings provided the information required for an estimate of the cross-correlation function, which was then Fourier transformed to yield the sound intensity spectrum. The method was validated using known stationary random signals, and the numerical simulation of a rotating source. The source spectrum in each case was successfully estimated despite leakage, a high variance, and a bias error in the intensity. The method was then applied to a mixed flow automotive cooling fan and the results were compared to flow measurements.
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Ju, Hongbin, and Fangyuan Zhong. "Near sound field analysis of rotating sources and its application in turbomachinery." In 34th Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1996. http://dx.doi.org/10.2514/6.1996-154.

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Hilfer, Michael, Maximilian Behn, Christian Klein, Thomas Ahlefeldt, Ulf Tapken, Lars Koop, and Lars Enghardt. "Near-field measurements of stationary and rotating in-duct sound sources with pressure-sensitive paint." In 28th AIAA/CEAS Aeroacoustics 2022 Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2022. http://dx.doi.org/10.2514/6.2022-3056.

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Shah, Parthiv N., Andrew White, Dan Hensley, Dimitri Papamoschou, and Håvard Vold. "Continuous-Scan Phased Array Measurement Methods for Turbofan Engine Acoustic Testing." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-77033.

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Imaging of aeroacoustic noise sources is routinely accomplished with geometrically fixed phased arrays of microphones. Several decades of research have gone into improvement and optimization of sensor layouts, selection of basis models, and deconvolution algorithms to produce sharper and more localized images of sound-producing regions in space. This paper explores an extension to conventional phased array measurements that uses slowly, continuously moving microphone arrays with and without coupling to rigid fixed arrays to improve image quality and better describe noise mechanisms on turbofan engine sources such as jet exhausts and turbomachinery components. Three approaches are compared in the paper: fixed receiver beamforming (FRBF), continuous-scan beamforming (CSBF), and multireference CSBF (MRCSBF). The third takes advantage of transfer function matrices formed between fixed and moving sensors to achieve effective virtual arrays with spatial density one to two orders of magnitude higher, with practical sensor budgets and scan speeds. The MRCSBF technique produces array sidelobe rejection that approaches the theoretical array pattern of a continuous 2-D aperture. The implications of this finding are that better source localization may be achieved with conventional delay and sum (DAS) beamforming (BF) with practical sensor budgets, and that an improved starting image of the sound source can be provided to deconvolution algorithms. These findings are demonstrated on analytical and experimental examples from a low-cost rotating phased array using point sound sources, as well as linear scanning array experiments of an impinging jets point source and a near-sonic jet nozzle exhaust.
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Tieghi, Lorenzo, Stefan Becker, Alessandro Corsini, Giovanni Delibra, Stefan Schoder, and Felix Czwielong. "Machine-Learning Clustering Methods Applied to Detection of Noise Sources in Low-Speed Axial Fan." In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-82116.

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Abstract The integration of rotating machineries in human-populated environments requires to limit noise emissions, with multiple aspects impacting on control of amplitude and frequency of the acoustic signature. This is a key issue to address and when combined with compliance of minimum efficiency grades, further complicates the design of axial fans. The aim of this research is to assess the capability of unsupervised learning techniques in unveiling the mechanisms that concur to the sound generation process in axial fans starting from high-fidelity simulations. To this aim, a numerical dataset was generated by means of LES simulation of a low-speed axial fan. The data set is enriched with sound source computed solving a-posteriori the perturbed convective wave equation (PCWE). First, the instantaneous flow features are associated to the sound sources through correlation matrices and then projected on latent basis to highlight the features with the highest importance. This analysis in also carried out on a reduced dataset, derived by considering two surfaces at 50% and 95% of the blade span. The sampled features on the surfaces are then exploited to train three cluster algorithms based on partitional, density and Gaussian criteria. The cluster algorithms are optimized and their results are compared, with the Gaussian Mixture one demonstrating the highest similarity (&gt; 80%). The derived clusters are analyzed, and the role of statistical distribution of velocity and pressure gradients is underlined. This suggests that design choices that affect these aspects may be beneficial to control the generation of noise sources.
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Liu, Pin, Yingzi Jin, Yanping Wang, Hongyu Qian, and Li Zhang. "Study on the Aerodynamic Performance of Small Axial Flow Counter-Rotating Fans." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-06091.

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Small axial flow fans are used as cooling components for computers, electronic equipments and other electronic components. With the increasing power of electrical equipment, the demand for lower noise and higher ventilation of cooling fans to improve heat transfer effects is also increasing. Traditional methods of improving ventilation by raising the fan’s rotation speed causes a decrease in efficiency and an increase in noise. The researchers have found that higher pressure, ventilation and efficiency can be achieved in a small space by counter-rotating fans than single fans. In this paper, 3D simulation has been done on flow field of counter-rotating fans for heat exchange, and the method of large eddy simulation (LES) and FW-H acoustic model have been used to simulate the distribution of noise field. The frequency spectrum from different sound sources has been analyzed, and the optimal ranges of the distance and gap between rotors have been determined. All that will provide a theoretical basis for researches on their characteristics and structure design.
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Asada, Kengo, Kimie Ito, Satoshi Sekimoto, Kozo Fujii, Masataka Koishi, and Toshiyuki Ikeda. "Analysis of Aeroacoustic Generated From a Rotating Tire With a Longitudinal Groove Using Large-Eddy Simulation." In ASME 2021 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/fedsm2021-66009.

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Abstract Flow fields obtained by large-eddy simulations around a rotating tire with the longitudinal groove are investigated to clarify the relationships between the shape parameters of the grooves and the directivity of aeroacoustic noise and to clarify noise sources. To obtain acoustic field around the rotating tire, the large-eddy simulations using the sixth-order compact finite difference scheme and the tridiagonal filter are performed. The four computational cases including the case without groove are considered in the present study. The proper orthogonal decomposition (POD) analysis revealed the distribution of bipolar modes that spread from the tire to the left and right. This result indicates two symmetrical sound sources near the front of the tire side surface regardless of the presence or absence of the groove shape. It is also found that the presence of grooves in the tire weakens the amplitude of the POD mode that spreads to the left and right. This fact is consistent with the fact that the sound pressure level on the lateral side of the tire weakens as the groove width widens. Based on the observation of the instantaneous field and these analyzes, the following is found. The noise-induced by the flow around the tire considered in the present study is emitted when the turbulent flow generated in front of the tire collides with the tire and flows along the tire’s side surface. Besides, when the tire has a groove, a part of the flow that collides with the tire flows into the groove so that the flow rate flowing on the side surface of the tire decreases and the noise itself also decreases. Therefore, the wider the tire’s groove width, the less noise is emitted from the tire’s lateral side.
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Papadopoulos, Christos I., and Ioannis T. Georgiou. "Structure-Excitation Modal Decoupling by Modification of the Involved Acoustic Modes of the Sound Insulating Enclosure." In ASME 2001 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/detc2001/vib-21412.

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Abstract Several noise sources such as machinery with rotating or reciprocating parts routinely produce high levels of noise in narrow frequency ranges lying in the neighbourhood of the rotating or reciprocating frequency and their harmonics. When enclosures are used to isolate such noise sources, peak response might be observed at these frequency ranges due both to increased excitation amplitude and resonating phenomena caused by the interaction of the excitation with the acoustic modes of the enclosure. Especially in the low frequency range and for low or intermediate wall absorption, the acoustic response of the enclosure is modal and these peak responses can be intense. This paper proposes a methodology to minimize the effect of narrow-frequency-band noise by redistribution of the acoustic modes of the insulating enclosure. This can be achieved by shifting the enclosure acoustic modes away from the excitation frequency so as to make superimposed resonating phenomena less intense. For that, several variable geometric modifications of the enclosure walls are introduced. The magnitude of those modifications that will lead to sparse mode distribution in the neighbourhood of the excitation frequency is estimated by means of a combined finite element-optimisation method. The above methodology is applied to an orthogonal enclosure and two different narrow-band loads in the neighbourhood of 90 and 120 Hz are studied. It is shown that, for each frequency load, a feasible set of geometric modifications can be found so as for the neighbouring modes to be shifted and, consecutively, for resonating effects to be made less intense. Furthermore it is shown that feasible solution to the problem of simultaneous control of noise having two or more intense excitation frequencies is also attainable.
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Benedek, Tamás, and János Vad. "Concerted Aerodynamic and Acoustic Diagnostics of an Axial Flow Industrial Fan, Involving the Phased Array Microphone Technique." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25916.

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The paper presents a methodology for on-site investigation of short-ducted industrial axial flow fans, as an easily realizable and effective means for concerted diagnostics on fan aerodynamics and acoustics along the rotor radius. The methodology relies on the accessibility of the fan from the upstream direction only. It involves experiments such as i) measurement of inlet axial velocity profile along the radius, combined with ii) beamforming studies using the Phased Array Microphone technique. The application of the methodology has been demonstrated in a case study of a ventilating fan. The semi-empirical data processing demonstrated significant changes of aerodynamic properties along the blade span. The acoustic studies regarded a frequency range being significant from the viewpoint of human audition. The phased array data have been processed and evaluated on the basis of two in-house developed beamforming codes, based on the Delay and Sum as well as the Rotating Source Identifier (ROSI) methods. The measurements revealed that the detected noise is dominated by rotating sources of broadband noise. By means of the ROSI code, pitchwise-resolved information has been obtained on the rotor noise. By such means, noise sources such as locally thickened suction side blade boundary layers and tip leakage flow have been identified. The spanwise variation of sound pressure has been compared with cascade loss indicators used in fan analysis and preliminary design, such as the total pressure loss coefficient and the Lieblein diffusion factor. The sound pressure has been found to increase locally with the total pressure loss and diffusion along the dominant portion of blade span, in the frequency bands being the most significant from the viewpoint of audibility of the noise generated by the fan.
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Danner, Florian, Christofer Kendall-Torry, and Hans-Peter Kau. "Aerodynamic Origin of Rotor-Rotor Interaction Noise From Unducted Propulsors." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-95572.

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The sound arising from blade row interaction in open rotor propulsion systems is known to significantly contribute to overall noise emissions. The present paper therefore addresses the origination of rotor-rotor interaction noise from a pair of unducted counter-rotating fans. The focus is on the aerodynamic mechanisms that involve sound generation, in order to provide the physical understanding required to find noise-reducing means. Detailed insight into the underlying phenomena is provided on the basis of numerical simulations applying the unsteady Reynolds-averaged Navier-Stokes equations. The interaction mechanisms are identified by extracting the time-dependent disturbances of the flow field in the respective rotor relative frame of reference. Conclusions on the sources of interaction noise and potential noise-reducing means are drawn by evaluating polar directivities, blade surface pressure distributions and propagation characteristics.
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