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Artykuły w czasopismach na temat „Directivity”

Autor: Grafiati

Data publikacji: 4 czerwca 2021

Data aktualizacji: 9 czerwca 2025

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1

Nakazawa, Toshiyasu, and Naoaki Shinohara. "Study on aircraft noise directivity of behind the start of takeoff roll." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 3 (August 1, 2021): 3202–8. http://dx.doi.org/10.3397/in-2021-2330.

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This paper discusses aircraft noise directivity behind the start of takeoff roll. Aircraft noise has the radiation directivity because of aircraft engine mount position and the engine noise directivity. Thus, lateral noise directivity correction is recommended in airport noise calculation guidelines such as ECAC Doc.29 and ICAO Doc9911. In these guidelines, the directivity of flyover noise and the directivity at the start of takeoff roll on ground are prepared separately. A 90-degree dipole model is used for the directivity of the flyover noise, and another similar directivity is used for the directivity behind the start of takeoff roll. It is necessary to properly evaluate the directivity behind the takeoff roll because it has a large contribution to noise calculation of the vicinity of the airport. Therefore, we measured aircraft noise behind the start of takeoff roll with sound level meters placed half-concentrically around Narita Airport in Japan. From these measurement results, various types of aircraft noise directivity behind the takeoff roll are examined and considered the effects of weather conditions such as wind direction. Finally the differences from existing models are compared.

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2

Sun, Xiaofang, Shisong Zhang, and Zhongshan Yao. "Directivity of spherical acoustic scattering based on COMSOL." Journal of Physics: Conference Series 2458, no. 1 (March 1, 2023): 012030. http://dx.doi.org/10.1088/1742-6596/2458/1/012030.

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Abstract The acoustic scattering characteristics of spheres are the basis for studying the sound scattering law of the target. The directivity of acoustic scattering is one of the most important characteristics of the target sound scattering law. In this paper, the acoustic scattering characteristics of rigid spheres and elastic spherical shells are analyzed from the two typical basic models of the rigid sphere and elastic spherical shell. The sound scattering directivity corresponding to different ka values under different models is analyzed by COMSOL finite element simulation analysis. The change law of spheroid scattering directivity of spheres under different elastic backgrounds of the rigid sphere and elastic spherical shell is compared and studied. It is found that the scattering directivity of both rigid spheres and elastic spherical shells will change with the change of ka value. The larger the ka, the stronger the forward directivity, and the more side lobes for rigid spheres. The backward directivity is greater than the forward directivity at ka≤1, while the forward directivity of the elastic spherical shell is always greater than the backward direction. And it is not difficult to find that the directivity of rigid spheres is relatively uniform in backward scattering when ka=1. When ka>1, the directivity increases with ka, the forward directivity becomes stronger and stronger, and the side lobes gradually increase. The elastic spherical shell uses air as the internal filler, and its directivity has always been forward than backward. The forward directivity also increases with the increase of ka, and the side lobes also increase with the increase of frequency.

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3

Trine, Allison, Margaret Miller, Emily Buss, G. Christopher Stecker, and Brian B. Monson. "Speech directivity patterns generated from a high-fidelity speech corpus." Journal of the Acoustical Society of America 153, no. 3_supplement (March 1, 2023): A292. http://dx.doi.org/10.1121/10.0018894.

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Human talkers are directional sound sources—a phenomenon that has consequences for speech perception in multi-talker environments. Directivity patterns for speech showing frequency- and angle-dependent radiation reveal that speech generally becomes more directional toward the front of the talker as frequency increases. Differences in physical attributes can lead to individual variability in directivity patterns across talkers. Here, we examine individual variability in speech directivity using frequency-dependentdirectivity indices and directivity maps. Speech directivity was examined in the horizontal plane using a corpus of simultaneous multi-channelfull-bandwidth (48-kHz sampling rate) recordings of the Bamford-Kowal-Bench (BKB) sentences recorded in an anechoic chamber. Thirty subjects (15 female) were recorded. The long-term average speech spectrum was utilized to calculate directivity indices in 1-ERB (equivalent rectangular bandwidth) bands. Gender differences in directivity indices were evaluated using a linear mixed-effects model. There was no main effect of gender. There was a main effect of ERB band with higher-frequency bands tending to have higher (i.e., more directional) directivity indices, however there was a nonmonotonic relationship between average directivity indices and frequency. Directivity maps demonstrated individual differences in speech radiation. [Work supported by NIH under Grant No. R01-DC019745.]

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4

Zhao, Guozhu, Kaibo Shi, and Shouming Zhong. "Research on Array Structures of Acoustic Directional Transducer." Mathematical Problems in Engineering 2021 (January 2, 2021): 1–5. http://dx.doi.org/10.1155/2021/6670277.

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This paper focuses on the directivity design of array structures of acoustic directional transducers. Based on Huygens principles, the directivity formula of transducer arrays under random distribution in xyz space is derived when the circular piston transducers are used as the array element, which is used to analyze the directivity and acoustic pressure of conical transducer arrangements. In addition, a practical approach to analyze the directivity and acoustic pressure of transducer arrays under random arrangements is proposed. Findings. The conical transducer arrays show side lobes at higher frequency. Below the frequency of 2 kHz, array directivity shows rapid changes. Above the frequency of 2 kHz, array directivity varies slowly with frequency. Besides, the beam width is Θ − 3 dB ≤ 29.85 ° .

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5

Musset, S., M. Maksimovic, E. Kontar, V. Krupar, N. Chrysaphi, X. Bonnin, A. Vecchio, et al. "Simulations of radio-wave anisotropic scattering to interpret type III radio burst data from Solar Orbiter, Parker Solar Probe, STEREO, and Wind." Astronomy & Astrophysics 656 (December 2021): A34. http://dx.doi.org/10.1051/0004-6361/202140998.

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Aims. We use multi-spacecraft observations of individual type III radio bursts to calculate the directivity of the radio emission. We compare these data to the results of ray-tracing simulations of the radio-wave propagation and probe the plasma properties of the inner heliosphere. Methods. We used ray-tracing simulations of radio-wave propagation with anisotropic scattering on density inhomogeneities to study the directivity of radio emissions. Simultaneous observations of type III radio bursts by four widely separated spacecraft were used to calculate the directivity and position of the radio sources. The shape of the directivity pattern deduced for individual events is compared to the directivity pattern resulting from the ray-tracing simulations. Results. We show that simultaneous observations of type radio III bursts by four different probes provide an opportunity to estimate the radio source positions and the directivity of the radio emission. The shape of the directivity varies from one event to another and it is consistent with anisotropic scattering of the radio waves.

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6

O'Donoghue, Jennifer L., and Karen R. Strobel. "Directivity and Freedom." American Behavioral Scientist 51, no. 3 (November 2007): 465–85. http://dx.doi.org/10.1177/0002764207306071.

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7

Dittberner, Andrew B. "Quantifying microphone directivity." Hearing Journal 56, no. 11 (November 2003): 22. http://dx.doi.org/10.1097/01.hj.0000292901.09293.7b.

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8

Jers, Harald. "Directivity of singers." Journal of the Acoustical Society of America 118, no. 3 (September 2005): 2008. http://dx.doi.org/10.1121/1.4785700.

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9

Johnston, James David. "Perceptual speaker directivity." Journal of the Acoustical Society of America 120, no. 4 (2006): 1763. http://dx.doi.org/10.1121/1.2372346.

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10

Yatabe, Kohei. "Modeling source directivity by solving inverse problems." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, no. 2 (November 30, 2023): 6088–91. http://dx.doi.org/10.3397/in_2023_0894.

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Directivity is an important property of a sound source in the real world. Howerver, majority of the wave-based acoustic simulation does not reflect directivity of a source. One of the reasons is that modeling of source directivity is not a simple task and remains a matter of research. In this talk, our attempts of modeling source directivity in time or frequency domains are briefly introduced.

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11

Liu, Hong, and Guo Zhu Zhao. "Two Methods to Test Transducer Array Directivity." Advanced Materials Research 912-914 (April 2014): 1485–88. http://dx.doi.org/10.4028/www.scientific.net/amr.912-914.1485.

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An array which possess more array element number and whose frequency of the drive signal can be as large as possible in a range, directivity will be more preferable. On the other hand, when the structure of the sound radiating surface of the transducer or array layout is symmetrical, the corresponding directivity pattern will be symmetrical. In order to test transducer directivity, two methods are designed. The one is to measure the ultrasonic sound pressure level by instruments. The sound pressure level is measured at multiple points to deduce the directivity angle of the acoustic transducer array. The beam width of the 3×3 array is about at 23kHz, and the directivity acute angle is about 10°; higher frequencies will lead to the side lobes, but it can be negligible when compared to the main lobe. The other method is using the frequency analyzer to test transducer directivity in a silencer chamber. The sound pressure level can be read out from frequency response diagrams. The angle between the sound pressure value that decreasing 3db from the max value 111.7db and the max value is about 11°. So the directivity acute angle is about 11°. It should be noticed that, as the directivity diagram can not be directly attributed, there is some deviation in the conclusion.

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12

Du, Bokai, Qun Yan, Ningjuan Dong, Qing Xue, and Yixiao Cheng. "Active noise control with variable directivity loudspeakers." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, no. 6 (November 30, 2023): 2756–61. http://dx.doi.org/10.3397/in_2023_0401.

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Active noise control (ANC) is an effective way to reduce the low frequency noise level for passengers in cars or aircrafts. In these applications, secondary sources are usually monopole loudspeakers. Variable directivity loudspeaker is a kind of loudspeaker which is able to control its own radiation directivity. It is potential to be able to control the sound field better compared monopole loudspeaker. Inspired by this, variable directivity loudspeakers are applied to an ANC system. A simulation is conducted to investigate the performance of the ANC system with variable directivity loudspeakers. Simulation results show that the ANC system with variable directivity loudspeakers outperforms the one with monopole loudspeakers in noise control using the same number of loudspeakers.

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13

Zhao, Guo Zhu, and Li Xuan Ma. "Research on the High-Power Directional Acoustic Transducer." Advanced Materials Research 912-914 (April 2014): 753–56. http://dx.doi.org/10.4028/www.scientific.net/amr.912-914.753.

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Through studying how to affect acoustic directivity with MATLAB software, it show that selection of a relatively larger surface of the transducer and a relatively closer transducer interval will be more preferable for directivity. While an array which possess more array element number and whose frequency of the drive signal can be as large as possible in a range, directivity will be more preferable. On the other hand, when the structure of the sound radiating surface of the transducer or array layout is symmetrical, the corresponding directivity pattern will be symmetrical. At a frequency of 10kHz, the individual rare earth magnetostrictive transducers its first point of the simulation carried out before the test. Sounding board with aluminum by the method used to improve the sound source diameter. With the sound plate diameter incrementing, the smaller the angle of the directivity. The beam width of the 3×3 array is about at 23kHz, and the directivity acute angle is about 10°, with a sounding board by the method used to improve their the diameter of the sound source, so as to realize the sound has directivity is feasible.

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14

Bellows, Samuel D., and Timothy W. Leishman. "Modeling musician diffraction for artificially excited clarinet directivity measurements." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A157. http://dx.doi.org/10.1121/10.0010960.

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Directivity measurements of musical instruments have many applications in musical, audio, and architectural acoustics. Typical measurement methods include artificially excited instruments and instruments played by live musicians. While recent advances in directivity measurement techniques enable higher resolutions for played instruments, the results are still limited in bandwidth and repeatability compared with directivity results from artificially excited instruments. However, artificially excited instruments typically neglect musician diffraction and absorption. This work compares possible approaches for representing musician diffraction in artificially excited clarinet measurements to improve their directivity results for room simulations or auralizations.

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15

Mathews, Logan T., Hunter J. Pratt, Mark C. Anderson, and Kent L. Gee. "Directivity and sound power of rockets: A comparative analysis of source characteristics and their implementation into a predictive model." Journal of the Acoustical Society of America 154, no. 4_supplement (October 1, 2023): A347. http://dx.doi.org/10.1121/10.0023752.

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Fundamental jet and rocket noise modeling includes quantifying the acoustic power and directivity characteristics of the source. While many attempts have been made to define a model for the sound power and directivity of jets and rockets, many of these models have been based on flawed measurements or methodologies. This paper presents the directivity and sound power characteristics as obtained from launched rockets. The results are compared with those in the literature. The directivity and sound power properties are used in a standard source model for rocket noise, and the resulting predictions are evaluated.

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16

Spudich, Paul, Badie Rowshandel, Shrey K. Shahi, Jack W. Baker, and Brian S. J. Chiou. "Comparison of NGA-West2 Directivity Models." Earthquake Spectra 30, no. 3 (August 2014): 1199–221. http://dx.doi.org/10.1193/080313eqs222m.

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Five directivity models have been developed based on data from the NGA-West2 database and based on numerical simulations of large strike-slip and reverse-slip earthquakes. All models avoid the use of normalized rupture dimension, enabling them to scale up to the largest earthquakes in a physically reasonable way. Four of the five models are explicitly “narrow-band” (in which the effect of directivity is maximum at a specific period that is a function of earthquake magnitude). Several strategies for determining the zero-level for directivity have been developed. We show comparisons of maps of the directivity amplification. This comparison suggests that the predicted geographic distributions of directivity amplification are dominated by effects of the models’ assumptions, and more than one model should be used for ruptures dipping less than about 65 degrees.

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17

Pavill, Hanna, and Micah Shepherd. "The sound radiation and directivity of glockenspiel bars." Journal of the Acoustical Society of America 155, no. 3_Supplement (March 1, 2024): A254. http://dx.doi.org/10.1121/10.0027407.

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The directivity of a musical instrument describes the predominant directions that sound radiates from that instrument when it is being played. The shape of an instrument, as well as the note and playing style, can greatly affect its sound radiation and directivity. The glockenspiel is a percussion instrument made of pitched metal bars of uniform thickness laid out in a keyboard pattern and set on a frame. It produces sound when the player strikes the bars with a mallet. Uniform beam theory is often used to describe the modal behavior of the individual glockenspiel bars. However, when a single bar is stuck, the other surrounding bars and support frame influence the sound radiation and directivity. Therefore, glockenspiel measurements were performed using a directivity measurement system which has previously been used to measure musical instrument directivity. To eliminate strike-to-strike variance, an automatic striking device was used. This work will compare the sound radiation and directivity of a glockenspiel bar in the standard configuration, to an individual glockenspiel bar outside of the frame.

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18

Zhou, R., and L. Shafai. "Directivity enhancement by layered radomes." Canadian Journal of Physics 73, no. 7-8 (July 1, 1995): 444–51. http://dx.doi.org/10.1139/p95-064.

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Single and layered radomes are often used to protect radiating elements. A two-dimensional analysis is used to investigate their influence on the antenna directivity and radiation patterns. Image-theory and integral-equation methods are used to formulate the problem for a line source and layered dielectrics of finite length over a ground plane, and solved numerically using the moment method. It is shown that, for a sufficiently long single-layer slab, the directivity enhancement is approximately equal to the square root of its relative permittivity. Properly truncating the slab can even improve the directivity. The optimum length of a finite dielectric slab is determined to maximize the directivity. For multilayer slabs, the directivity enhancement is much greater and they can be used with low-permittivity dielectrics to simulate a single-layer one of higher permittivity. Frequency dependency of the enhanced gain is also studied. Useful information for how to incorporate the radome parameters into the antenna design and use it for gain or directivity enhancement is provided.

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19

Pörschmann, Christoph, and Johannes M. Arend. "Effects of hand postures on voice directivity." JASA Express Letters 2, no. 3 (March 2022): 035203. http://dx.doi.org/10.1121/10.0009748.

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While speaking, hand postures, such as holding a hand in front of the mouth or cupping the hands around the mouth, influence human voice directivity. This study presents and analyzes spherical voice directivity datasets of an articulated [a] with and without hand postures. The datasets were determined from measurements with 13 subjects in a surrounding spherical microphone array with 32 microphones and then upsampled to a higher spatial resolution. The results show that hand postures strongly impact voice directivity and affect the directivity index by up to 6 dB, which is more than variances caused by phoneme-dependent differences.

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20

Liu, Qingxi, Wenhua Song, Ye Tian, Zeying Zhang, and Guang Yuan. "On the Reproducibility and Directionality of Underwater Laser-induced Acoustic Signal." Journal of Physics: Conference Series 2486, no. 1 (May 1, 2023): 012064. http://dx.doi.org/10.1088/1742-6596/2486/1/012064.

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Abstract An intense laser pulse focused in water could induce plasma expansion, which can be used as an impulsive sound source. The optoacoustic underwater source is very useful in marine applications; however, the poor reproductivity and the sharp directivity of the emitted signals is a big problem. The reproductivity and directivity of the acoustic emission by laser breakdown are measured in the laboratory experiment in this paper, and the results show that the reproductivity and directivity are both direction-dependent. The measurement also shows the feasibility of improving the reproductivity and directivity by adjusting the focusing system of the laser beam.

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21

Pezzoli, Mirco, Antonio Canclini, Fabio Antonacci, and Augusto Sarti. "A comparative analysis of the directional sound radiation of historical violins." Journal of the Acoustical Society of America 152, no. 1 (July 2022): 354–67. http://dx.doi.org/10.1121/10.0012577.

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The directivity pattern of a musical instrument describes the sound energy radiation as a function of frequency and direction of emission. Violins exhibit a rather complex directivity pattern, which is known to show rapid variations across frequencies, and whose behavior cannot be easily predicted except in the lowest frequency range. The acoustic behavior of the violin is a fascinating research topic that has prompted numerous published works, but a thorough, comprehensive, and comparative analysis of violin directivity patterns is long overdue. In this article, we propose a set of metrics for characterizing the radiative behavior of musical instruments and, in particular, for comparing their directivity patterns. We apply such metrics for a comparative analysis of the directivity patterns of some of the most prestigious historical violins ever made, including grand masters such as Antonio Stradivari, Giuseppe Guarneri “del Gesú” and members of the Amati family. The instruments are preserved in the Violin Museum of Cremona, Italy, where our lab is located. The analysis methodology introduced in this work allowed us to quantitatively evaluate the similarity of directivity patterns of such extraordinary instruments and draw some interesting conclusions.

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22

Xie, Junju. "Strong‐Motion Directionality and Evidence of Rupture Directivity Effects during the Chi‐Chi Mw 7.6 Earthquake." Bulletin of the Seismological Society of America 109, no. 6 (October 29, 2019): 2367–83. http://dx.doi.org/10.1785/0120190087.

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Abstract This article investigates the spatial distribution, predominant direction, and variations in the intensity measures (IMs) with orientation for classified pulse‐like and nonpulse motions during Chi‐Chi Mw 7.6 earthquake. The results show evidence of high polarization for long‐period spectral accelerations at relatively large source‐to‐site distances (50–100 km) north of the Chelungpu fault. The polarization of long‐period motions shows a clear correlation with the directivity parameters’ isochrone directivity predictor and ξ, indicating a connection between directionality and rupture directivity. The variation in strong‐motion directionality with the period is also studied. The discrepancy in directionality caused by strong directivity increases with the period from 1 to 10 s, which confirms a clear correlation of period‐dependent directionality with directivity effects. This study finds stronger directionality of pulse‐like motions than nonpulse motions for long periods over 3 s with higher maximum‐to‐median and maximum‐to‐minimum IM ratios. For periods over 3 s, the maximum‐to‐median ratios of pulse‐like motions are higher than the mean prediction of the Shahi and Baker (2014a) model, whereas those of nonpulse motions are lower than the prediction. However, this study does not find simple and clear results for the directions of the maximum component at different periods for pulse‐like and nonpulse motions. Despite clear differences between the unidirectional fling‐step and bidirectional forward directivity pulses, the effects of fling‐step and forward directivity are actually coupled in the waveforms.

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23

Brandner, Manuel, Matthias Frank, and Alois Sontacchi. "Horizontal and Vertical Voice Directivity Characteristics of Sung Vowels in Classical Singing." Acoustics 4, no. 4 (October 1, 2022): 849–66. http://dx.doi.org/10.3390/acoustics4040051.

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Singing voice directivity for five sustained German vowels /a:/, /e:/, /i:/, /o:/, /u:/ over a wide pitch range was investigated using a multichannel microphone array with high spatial resolution along the horizontal and vertical axes. A newly created dataset allows to examine voice directivity in classical singing with high resolution in angle and frequency. Three voice production modes (phonation modes) modal, breathy, and pressed that could affect the used mouth opening and voice directivity were investigated. We present detailed results for singing voice directivity and introduce metrics to discuss the differences of complex voice directivity patterns of the whole data in a more compact form. Differences were found between vowels, pitch, and gender (voice types with corresponding vocal range). Differences between the vowels /a:, e:, i:/ and /o:, u:/ and pitch can be addressed by simplified metrics up to about d2/D5/587 Hz, but we found that voice directivity generally depends strongly on pitch. Minor differences were found between voice production modes and found to be more pronounced for female singers. Voice directivity differs at low pitch between vowels with front vowels being most directional. We found that which of the front vowels is most directional depends on the evaluated pitch. This seems to be related to the complex radiation pattern of the human voice, which involves a large inter-subjective variability strongly influenced by the shape of the torso, head, and mouth. All recorded classical sung vowels at high pitches exhibit similar high directionality.

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Bradley, Brendon A., and Graeme Weatherill. "Consideration of near-fault effects in New Zealand seismic hazard analysis and design spectra." Bulletin of the New Zealand Society for Earthquake Engineering 58, no. 2 (June 1, 2025): 108–17. https://doi.org/10.5459/bnzsee.1743.

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This paper examines the manner in which near-fault ground-motion phenomena are considered in the probabilistic seismic hazard analysis underpinning the 2022 New Zealand National Seismic Hazard Model (NZ NSHM), and its subsequent codification in the draft Technical Specification TS1170.5:2004. Directivity is already implicitly considered in the 2022 NSHM, and thus the ‘baseline’ draft TS1170.5 spectra, before any additional near-fault factor is applied. Specific studies in NZ and California suggest that explicit modelling of directivity could result in increases of up to 15-20% for 2475-year return period SA(T = 3:0s) values for ‘directivity-prone locations’, but are more likely to be on the order of 10% when a weighted average of multiple directivity models is considered. In contrast, the NZS1170.5:2004 near-fault factor, N(T;D), results in a 36% increase for small source-to-site distances. Hence, either: (1) the NZS1170.5:2004 near-fault factor should be removed so that directivity is implicitly considered in the hazard, which is consistent with other international codes, and also consistent with the implicit treatment of deep sedimentary basin effects in the 2022 NSHM, or (2) a parametric revision of the near-fault factor is needed that results in approximately a four-fold reduction in its size. Obtaining a more precise quantification of directivity effects is complicated by multi-segment ruptures in contemporary seismic source models, and the large uncertainty in predicted directivity modification factors from the alternative existing models.

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KOYAMA, Junji. "Short Period Seismic Directivity." Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 40, no. 3 (1987): 397–404. http://dx.doi.org/10.4294/zisin1948.40.3_397.

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Oyaba, Takashi. "Speaker system having directivity." Journal of the Acoustical Society of America 93, no. 3 (March 1993): 1680. http://dx.doi.org/10.1121/1.406748.

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Oyaba, Takashi. "Speaker system having directivity." Journal of the Acoustical Society of America 91, no. 2 (February 1992): 1200. http://dx.doi.org/10.1121/1.402556.

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Harrell, Jefferson A., and Elmer L. Hixson. "Constant directivity loudspeaker arrays." Journal of the Acoustical Society of America 91, no. 4 (April 1992): 2326. http://dx.doi.org/10.1121/1.403523.

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Williams, J. Michael, Michael D. Cerna, and Elmer L. Hixson. "Constant directivity receiving arrays." Journal of the Acoustical Society of America 91, no. 4 (April 1992): 2325. http://dx.doi.org/10.1121/1.403546.

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Chu, Wing T., Alf Warnock, and Jean‐Charles Guy. "Directivity of human talkers." Journal of the Acoustical Society of America 110, no. 5 (November 2001): 2664. http://dx.doi.org/10.1121/1.4777091.

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Leishman, Timothy W., and Samuel D. Bellows. "Musical instrument directivity measurements." Journal of the Acoustical Society of America 146, no. 4 (October 2019): 2822. http://dx.doi.org/10.1121/1.5136777.

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Pozar, D. "Directivity of omnidirectional antennas." IEEE Antennas and Propagation Magazine 35, no. 5 (October 1993): 50–51. http://dx.doi.org/10.1109/74.242180.

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Schejbal, V., J. D. Mahoney, and N. McDonald. "Directivity of planar antennas." IEEE Antennas and Propagation Magazine 41, no. 2 (April 1999): 60–65. http://dx.doi.org/10.1109/74.769693.

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Bulgakovа, A. A., N. N. Gorobets, V. A. Katrich, and V. A. Lyashchenko. "DIRECTIVITY OF ANTENNA ARRAYS." Radio physics and radio astronomy 21, no. 4 (December 5, 2016): 285–97. http://dx.doi.org/10.15407/rpra21.04.285.

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Bodley, Martin Reed. "High directivity microphone array." Journal of the Acoustical Society of America 113, no. 6 (2003): 2957. http://dx.doi.org/10.1121/1.1588802.

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Bodley, Martin Reed. "High directivity microphone array." Journal of the Acoustical Society of America 116, no. 6 (2004): 3246. http://dx.doi.org/10.1121/1.1852937.

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Bodley, Martin Reed. "High directivity microphone array." Journal of the Acoustical Society of America 120, no. 1 (2006): 18. http://dx.doi.org/10.1121/1.2227659.

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Murphy, David John. "Constant directivity acoustic horn." Journal of the Acoustical Society of America 121, no. 1 (2007): 14. http://dx.doi.org/10.1121/1.2434265.

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Hansen, R. C. "Directivity of ring arrays." Microwave and Optical Technology Letters 18, no. 6 (August 20, 1998): 370–75. http://dx.doi.org/10.1002/(sici)1098-2760(19980820)18:6<370::aid-mop2>3.0.co;2-a.

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Pinchera, Daniele. "On the Trade-Off between the Main Parameters of Planar Antenna Arrays." Electronics 9, no. 5 (April 30, 2020): 739. http://dx.doi.org/10.3390/electronics9050739.

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The aim of this paper is two-fold. First, the trade-off between directivity, beam-width, side-lobe-level, number of radiating elements, and scanning range of planar antenna arrays is reviewed, and some simple ready-to-use formulas for the preliminary dimensioning of equispaced planar arrays are provided. Furthermore, the synthesis of sparse planar arrays, and the issue of their reduction in directivity, is analyzed. Second, a simple, yet effective, novel approach to overcome the directivity issue is proposed. The presented method is validated by several synthesized layouts; the examples show that it is possible to synthesize sparse arrays, able to challenge with equispaced lattices in terms of directivity, with a significant reduction of the number of radiators.

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41

Xu, Long Jun, and Sheng Chao Yang. "Near-Fault Directivity Spectrum for Nuclear Structure Design on Rock Site." Advanced Materials Research 243-249 (May 2011): 3820–23. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.3820.

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This study is aimed at evaluating the safety implications of near-fault directivity effect on nuclear structure and facilities designed according to the Chinese code. To this end, a set of near-fault ground motions at rock site with typical forward-directivity effect is examined with emphasis on several key parameters and response spectra. The bi-normalized response spectra in terms of different corner periods are utilized to derive nuclear design spectra. It was concluded that nuclear design spectra on rock site derived from typical directivity records are significantly influenced by both magnitude and distance. The nuclear design spectra specified in the code need to be adjusted to reflect the near-fault directivity effect of large earthquakes.

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42

Seo, Min-Seong, Won-Young Kim, and YoungHee Kim. "Rupture Directivity of the 2021 ML 2.2 Gwangyang, Korea, Microearthquake: Toward Resolving High-Resolution Rupture Process of a Small Earthquake." Seismic Record 2, no. 4 (October 1, 2022): 227–36. http://dx.doi.org/10.1785/0320220030.

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Abstract Moderate-to-large earthquakes (M&gt;6) frequently show clear rupture directivity. Recent studies revealed that a substantial percentage of small-sized earthquakes (M&lt;∼5) display rupture directivity as well, owing to enhanced seismic monitoring. Is rupture directivity a common feature for earthquakes of all sizes? In this study, we investigated the rupture directivity of the 27 August 2021 ML 2.2 Gwangyang microearthquake that occurred at the southern tip of the Korean Peninsula by utilizing data from a recently expanded dense seismic network. The mainshock had two foreshocks and three aftershocks, which enabled us to define the fault plane from precise relative event locations and a well-constrained focal mechanism. Analysis of apparent source time functions obtained with the empirical Green’s function technique reveals that the mainshock ruptured unilaterally toward the east. A detailed analysis of the source pulse leaving the focal sphere in 3D indicates that rupture directivity is consistent with the fault geometry and slip direction. Our study demonstrates that we can resolve rupture directivity of unilaterally rupturing microearthquakes (M&lt;∼3) given adequate azimuthal coverage, and that this will lead to an improved understanding of the seismogenic processes in regions of low seismicity worldwide.

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Zhong, Jiaxin, Haishan Zou, Jing Lu, and Dong Zhang. "A modified convolution model for calculating the far field directivity of a parametric array loudspeaker." Journal of the Acoustical Society of America 153, no. 3 (March 2023): 1439–51. http://dx.doi.org/10.1121/10.0017361.

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The far field directivity is a straightforward indicator to describe the radiation pattern of the audio sound generated by a parametric array loudspeaker (pal), but its accurate and computationally efficient prediction is still challenging at present. This paper derives two-dimensional (2D), three-dimensional (3D), and 3D axisymmetric convolution models for calculating the far field directivity based on the quasilinear solution of Westervelt equation. The obtained expressions are expressed as linear and spherical convolutions of the ultrasound directivity and Westervelt directivity for 2D and 3D models, respectively. To improve prediction accuracy, the obtained expression is multiplied by an effective directivity resulted from the aperture factor of audio sound. The calculated directivities are compared against the exact solution obtained using the cylindrical and spherical wave expansions for 2D and 3D models, respectively. Numerical results with piston, apodized, and steerable profiles in both 2D and 3D models show that the proposed modified convolution model agrees well with the exact solution. It is also found that sidelobes appear in the audio sound directivity at large aperture sizes and high audio frequencies due to the aperture factor of audio sound, which can be predicted with the proposed method with a relatively low computational expenditure.

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Shrestha, Sujan, Hijab Zahra, Muhammad Ali Babar Abbasi, Mohsen Asadnia, and Syed Muzahir Abbas. "Increasing the Directivity of Resonant Cavity Antennas with Nearfield Transformation Meta-Structure Realized with Stereolithograpy." Electronics 10, no. 3 (February 1, 2021): 333. http://dx.doi.org/10.3390/electronics10030333.

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A simple, nearfield transformation meta-structure is proposed to increase the directivity of resonant cavity antennas (RCA). The meta-structure is comprised of 14 × 14 meta-atoms or so called “unit-cells”, adding localized phase delays in the aperture of the RCA and thus increasing its broadside directivity. A prototype of the meta-structure is additively manufactured using the stereolithograpy process and has a profile of 0.56λ. With the meta-structure integrated with the RCA, it demonstrates a measured broadside directivity of 20.15 dBi without affecting its half-power directivity bandwidth. Benefiting from additive manufacturing, the proposed approach is a simple, light-weight, low-cost, and planar approach that can be tailored to achieve medium-to-high gains with RCAs.

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Zhao, Liuxian, Lihua Tang, Yuxin Liu, Zhaoyong Sun, Qimin Liu, and Chuanxing Bi. "Passive directivity detection of acoustic sources based on acoustic Luneburg lens." Journal of the Acoustical Society of America 154, no. 2 (August 1, 2023): 594–601. http://dx.doi.org/10.1121/10.0020541.

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This article reports an acoustic Luneburg lens (ALL) design with graded refractive index for passive directivity detection of acoustic sources. The refractive index profile of the lens is realized based on square pillars with graded variation of their dimensions. Numerical and experimental studies are conducted to investigate the performance of directivity detection. The results demonstrate that the lens designed and developed in this study is capable of precisely detecting the directivity of one acoustic source. Furthermore, the directivities of two acoustic sources can also be detected with a resolution of 15°. In addition, different methods are investigated, including introducing phase difference by tuning input signals or moving ALL, and increasing the aperture size of ALL, to improve the resolution of dual sources directivity detection.

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Song, Zhongchang, Chuang Zhang, Weijie Fu, Zhanyuan Gao, Wenzhan Ou, Jinhu Zhang, and Yu Zhang. "Investigation on whistle directivity in the Indo-Pacific humpback dolphin (Sousa chinensis) through numerical modeling." Journal of the Acoustical Society of America 151, no. 6 (June 2022): 3573–79. http://dx.doi.org/10.1121/10.0011513.

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Odontocetes have evolved special acoustic structures in the forehead to modulate echolocation and communication signals into directional beams to facilitate feeding and social behaviors. Whistle directivity was addressed for the Indo-Pacific humpback dolphin ( Sousa chinensis) by developing numerical models in the current paper. Directivity was first examined at the fundamental frequency 5 kHz, and simulations were then extended to the harmonics of 10, 15, 20, 25, and 30 kHz. At 5 kHz, the –3 dB beam widths in the vertical and horizontal planes were 149.3° and 119.4°, corresponding to the directivity indexes (DIs) of 4.4 and 5.4 dB, respectively. More importantly, we incorporated directivity of the fundamental frequency and harmonics to produce an overall beam, resulting in −3 dB beam widths of 77.2° and 62.9° and DIs of 8.2 and 9.7 dB in the vertical and horizontal planes, respectively. Harmonics can enhance the directivity of fundamental frequency by 3.8 and 4.3 dB, respectively. These results suggested the transmission system can modulate whistles into directional projection, and harmonics can improve DI.

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Sonasang, Somchat, and Niwat Angkawisittpan. "Design of Microstrip Parallel-Coupled Lines with High Directivity using Symmetric-Centered Inductors." Applied Computational Electromagnetics Society 36, no. 6 (August 6, 2021): 657–63. http://dx.doi.org/10.47037/2020.aces.j.360606.

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A technique for directivity improvement of the microstrip parallel-coupled lines using symmetric-centered inductors is presented in this paper. The design procedure of the symmetric-centered inductors using the closed-form equations is given. The proposed technique was performed with a design at the operating frequency of 0.9 GHz on an FR4 substrate. Validity of the proposed technique is verified by simulations and measurements in comparisons with conventional parallel-coupled lines. The measured results exhibit the isolation of -30.10 dB and directivity of 19.28 dB at the operating frequency of 0.9 GHz. The directivity from the measured results is improved by more than 4 dB at 0.9 GHz and more than 6 dB at 1.05 GHz compared with the conventional parallel-coupled lines. In addition, the proposed technique for the microstrip parallel-coupled line can achieve a high directivity with the compact size (21.0 mm x 4.70 mm). The novelty of this paper is by introducing the proposed and closed-form design equations for the compact symmetric-centered inductors with high directivity.

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Zhang, Wen, Hui Zhang, Shijiu Jin, and Zhoumo Zeng. "A Two-Dimensional CMUT Linear Array for Underwater Applications: Directivity Analysis and Design Optimization." Journal of Sensors 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/5298197.

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Capacitive micromachined ultrasonic transducers (CMUTs) are one of the promising MEMS devices. This paper proposed an integrated vibration membrane structure to design a two-dimensional CMUT linear array for underwater applications. The operation frequencies for different medium have been calculated and simulated, which are 2.5 MHz in air and 0.7 MHz in water. The directivity analyses for the CMUT cell, subarray, and linear array have been provided. According to the product theorems, the directivity function of the complex array is obtained using a combination of the directivity functions of certain simple structures. Results show that the directivity of a CMUT cell is weak due to the small size, but the directivity of the designed linear array is very strong. Influential parameters of the linear array have been discussed, including the cell numbers, the adjacent distance, and the operation medium. In order to further suppress the side lobe interference and improve the resolution and the imaging quality of the imaging system, several weighting methods are used for optimization and comparison. Satisfactory side lobe suppression results are obtained, which can meet the actual requirements.

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Pörschmann, Christoph, and Johannes M. Arend. "Investigating phoneme-dependencies of spherical voice directivity patterns II: Various groups of phonemes." Journal of the Acoustical Society of America 153, no. 1 (January 2023): 179–90. http://dx.doi.org/10.1121/10.0016821.

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The substantial variation between articulated phonemes is a fundamental feature of human voice production. However, while the spectral and temporal aspects of the phonemes have been extensively studied, few have investigated the spatial aspects and analyzed phoneme-dependent differences in voice directivity. This paper extends our previous research focusing on the directivity patterns of selected vowels and fricatives [Pörschmann and Arend, J. Acoust. Soc. Am. 149(6), 4553–4564 (2021)] and examines different groups of phonemes, such as plosives, nasals, voiced alveolars, and additional fricatives. For this purpose, full-spherical voice directivity measurements were performed for 13 persons while they articulated the respective phonemes. The sound radiation was recorded simultaneously using a surrounding spherical microphone array with 32 microphones and then spatially upsampled to a dense sampling grid. Based on these upsampled datasets, the spherical voice directivity was studied, and phoneme-dependent variations were analyzed. The results show significant differences between the groups of phonemes. However, within three groups (plosives, nasals, and voiced alveolars), the differences are small, and the variations in the directivity index were statistically insignificant.

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Makino, Yusuke, and Yasushi Takano. "Sound source directivity considering source movement." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 265, no. 4 (February 1, 2023): 3579–89. http://dx.doi.org/10.3397/in_2022_0505.

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When the source moves, frequency modulation (Doppler effect) occurs in the radiated sound, and the directivity of source changes. In addition, the source can be not located in a direction from the direction of arrival of radiated sound. Therefore, the sound pressure directivity may differ depending on whether the source is static or moving. There are two types of wave equations, one that describes sound pressure as a variable and one that describes velocity potential as a variable. When the sound source moves at a constant velocity and the equation is solved assuming that the source strength is constant with respect to the velocity, the sound pressure directivity of the radiated sound changes depending on the description method of the wave equation. The sound pressure was obtained by solving the wave equations where a single monopole source and a dipole source are moving at a constant velocity. From the results, we showed the difference of sound pressure directivity when source is moving from the directivity of static source.

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