The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform

D. Dallet - One of the best experts on this subject based on the ideXlab platform.

  • Practical supergrain head sized arrays
    1997 IEEE International Conference on Acoustics Speech and Signal Processing, 1997
    Co-Authors: D. Masmoudi, D. Dallet
    Abstract:

    This paper carried out a new design of head sized sensor arrays with a simple delay-and-sum beamforming which provides useful amounts of Directivity Index with sufficient robustness to errors. A frequency-independent sidelobe reduction is proposed to achieve optimal frequency characteristics. In order to obtain this control, a principle of combining multiple level of array structures is established. Results are presented for spherically isotropic noise. It is found that good performance can be obtained for a head sized array by combining multiple level structures with simple delay and sum beamformer.

  • ICASSP - Practical supergrain head sized arrays
    1997 IEEE International Conference on Acoustics Speech and Signal Processing, 1997
    Co-Authors: D. Masmoudi, D. Dallet
    Abstract:

    This paper carried out a new design of head sized sensor arrays with a simple delay-and-sum beamforming which provides useful amounts of Directivity Index with sufficient robustness to errors. A frequency-independent sidelobe reduction is proposed to achieve optimal frequency characteristics. In order to obtain this control, a principle of combining multiple level of array structures is established. Results are presented for spherically isotropic noise. It is found that good performance can be obtained for a head sized array by combining multiple level structures with simple delay and sum beamformer.

D. Masmoudi - One of the best experts on this subject based on the ideXlab platform.

  • Practical supergrain head sized arrays
    1997 IEEE International Conference on Acoustics Speech and Signal Processing, 1997
    Co-Authors: D. Masmoudi, D. Dallet
    Abstract:

    This paper carried out a new design of head sized sensor arrays with a simple delay-and-sum beamforming which provides useful amounts of Directivity Index with sufficient robustness to errors. A frequency-independent sidelobe reduction is proposed to achieve optimal frequency characteristics. In order to obtain this control, a principle of combining multiple level of array structures is established. Results are presented for spherically isotropic noise. It is found that good performance can be obtained for a head sized array by combining multiple level structures with simple delay and sum beamformer.

  • ICASSP - Practical supergrain head sized arrays
    1997 IEEE International Conference on Acoustics Speech and Signal Processing, 1997
    Co-Authors: D. Masmoudi, D. Dallet
    Abstract:

    This paper carried out a new design of head sized sensor arrays with a simple delay-and-sum beamforming which provides useful amounts of Directivity Index with sufficient robustness to errors. A frequency-independent sidelobe reduction is proposed to achieve optimal frequency characteristics. In order to obtain this control, a principle of combining multiple level of array structures is established. Results are presented for spherically isotropic noise. It is found that good performance can be obtained for a head sized array by combining multiple level structures with simple delay and sum beamformer.

Peter T Madsen - One of the best experts on this subject based on the ideXlab platform.

  • Three-dimensional beam pattern of regular sperm whale clicks confirms bent-horn hypothesis.
    The Journal of the Acoustical Society of America, 2020
    Co-Authors: Walter M. X. Zimmer, Peter L. Tyack, Mark P. Johnson, Peter T Madsen
    Abstract:

    The three-dimensional beam pattern of a sperm whale (Physeter macrocephalus) tagged in the Ligurian Sea was derived using data on regular clicks from the tag and from hydrophones towed behind a ship circling the tagged whale. The tag defined the orientation of the whale, while sightings and beamformer data were used to locate the whale with respect to the ship. The existence of a narrow, forward-directed P1 beam with source levels exceeding 210 dBpeak re: 1 microPa at 1 m is confirmed. A modeled forward-beam pattern, that matches clicks >20 degrees off-axis, predicts a Directivity Index of 26.7 dB and source levels of up to 229 dBpeak re: 1 microPa at 1 m. A broader backward-directed beam is produced by the P0 pulse with source levels near 200 dBpeak re: 1 microPa at 1 m and a Directivity Index of 7.4 dB. A low-frequency component with source levels near 190 dBpeak re: 1 microPa at 1 m is generated at the onset of the P0 pulse by air resonance. The results support the bent-horn model of sound production in sperm whales. While the sperm whale nose appears primarily adapted to produce an intense forward-directed sonar signal, less-directional click components convey information to conspecifics, and give rise to echoes from the seafloor and the surface, which may be useful for orientation during dives.

  • Echolocation click source parameters of Australian snubfin dolphins (Orcaella heinsohni)
    Journal of the Acoustical Society of America, 2018
    Co-Authors: Mafalda De Freitas, Joshua N. Smith, Frants H. Jensen, Kristian Beedholm, Peter T Madsen
    Abstract:

    The Australian snubfin dolphin (Orcaella heinsohni) is endemic to Australian waters, yet little is known about its abundance and habitat use. To investigate the feasibility of Passive Acoustic Monitoring for snubfin dolphins, biosonar clicks were recorded in Cygnet Bay, Australia, using a four-element hydrophone array. Clicks had a mean source level of 200 ± 5 dB re 1 μPa pp, transmission Directivity Index of 24 dB, mean centroid frequency of 98 ± 9 kHz, and a root-mean-square bandwidth of 31 ± 3 kHz. Such properties lend themselves to passive acoustic monitoring, but are comparable to similarly-sized delphinids, thus requiring additional cues to discriminate between snubfins and sympatric species.The Australian snubfin dolphin (Orcaella heinsohni) is endemic to Australian waters, yet little is known about its abundance and habitat use. To investigate the feasibility of Passive Acoustic Monitoring for snubfin dolphins, biosonar clicks were recorded in Cygnet Bay, Australia, using a four-element hydrophone array. Clicks had a mean source level of 200 ± 5 dB re 1 μPa pp, transmission Directivity Index of 24 dB, mean centroid frequency of 98 ± 9 kHz, and a root-mean-square bandwidth of 31 ± 3 kHz. Such properties lend themselves to passive acoustic monitoring, but are comparable to similarly-sized delphinids, thus requiring additional cues to discriminate between snubfins and sympatric species.

  • three dimensional beam pattern of regular sperm whale clicks confirms bent horn hypothesis
    Journal of the Acoustical Society of America, 2005
    Co-Authors: Walter M. X. Zimmer, Peter L. Tyack, Mark P. Johnson, Peter T Madsen
    Abstract:

    The three-dimensional beam pattern of a sperm whale (Physeter macrocephalus) tagged in the Ligurian Sea was derived using data on regular clicks from the tag and from hydrophones towed behind a ship circling the tagged whale. The tag defined the orientation of the whale, while sightings and beamformer data were used to locate the whale with respect to the ship. The existence of a narrow, forward-directed P1 beam with source levels exceeding 210  dB peak re: 1 μPa at 1 m is confirmed. A modeled forward-beam pattern, that matches clicks >20° off-axis, predicts a Directivity Index of 26.7 dB and source levels of up to 229  dB peak re: 1 μPa at 1 m. A broader backward-directed beam is produced by the P0 pulse with source levels near 200  dB peak re: 1 μPa at 1 m and a Directivity Index of 7.4 dB. A low-frequency component with source levels near 190  dB peak re: 1 μPa at 1 m is generated at the onset of the P0 pulse by air resonance. The results support the bent-horn model of sound production in sperm whales. While the sperm whale nose appears primarily adapted to produce an intense forward-directed sonar signal, less-directional click components convey information to conspecifics, and give rise to echoes from the seafloor and the surface, which may be useful for orientation during dives.

Hu Zhang - One of the best experts on this subject based on the ideXlab platform.

  • A low-frequency superdirective acoustic vector sensor array
    2015 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2015
    Co-Authors: Shie Yang, Hu Zhang
    Abstract:

    This paper provides a novel acoustic vector sensor array architecture for superDirectivity at low frequencies. It has a uniform 3 by 3 rectangular geometry of intersensor spacing less than 0.04 wavelength over its operation frequency band, with an up to 10.4 dB of Directivity Index in cylindrically isotropic noise. This is realized through a mode domain approach, which accesses the acoustic modes by fitting certain multipole models to the wavefield observations. Field experiments show that this is a practical solution of implementing a miniaturized vector sensor array with superDirectivity.

  • ICASSP - A low-frequency superdirective acoustic vector sensor array
    2015 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2015
    Co-Authors: Shie Yang, Hu Zhang
    Abstract:

    This paper provides a novel acoustic vector sensor array architecture for superDirectivity at low frequencies. It has a uniform 3 by 3 rectangular geometry of intersensor spacing less than 0.04 wavelength over its operation frequency band, with an up to 10.4 dB of Directivity Index in cylindrically isotropic noise. This is realized through a mode domain approach, which accesses the acoustic modes by fitting certain multipole models to the wavefield observations. Field experiments show that this is a practical solution of implementing a miniaturized vector sensor array with superDirectivity.

Ruth A. Bentler - One of the best experts on this subject based on the ideXlab platform.

  • a method to measure hearing aid Directivity Index and polar pattern in small and reverberant enclosures
    International Journal of Audiology, 2011
    Co-Authors: Yu Hsiang Wu, Ruth A. Bentler
    Abstract:

    AbstractObjective: The Directivity Index (DI) and polar pattern of directional hearing aids are typically measured in an anechoic chamber, which is expensive and not commonly found. This article proposes a quasi-anechoic technique to measure hearing aid Directivity in small and reverberant enclosures using the root-mean-square amplitude of the first 3 ms of the hearing aid's response to the input signal. Design: The hearing aid's planar DI and polar pattern were measured using the proposed method in an audiologic booth with low reverberation, a room with moderate reverberation, and an anechoic chamber. The measurement was repeated four times for each aid in each environment. The results were compared to the Directivity obtained in the anechoic chamber using two benchmark measurements. Study Sample: Eight hearing aids with a fixed directional mode were tested. Results and Conclusions: The results revealed that the error of the proposed method in DI was smaller than 0.3 dB in 94% of the measurement conditio...

  • A method to measure hearing aid Directivity Index and polar pattern in small and reverberant enclosures
    International Journal of Audiology, 2011
    Co-Authors: Yu Hsiang Wu, Ruth A. Bentler
    Abstract:

    OBJECTIVE: The Directivity Index (DI) and polar pattern of directional hearing aids are typically measured in an anechoic chamber, which is expensive and not commonly found. This article proposes a quasi-anechoic technique to measure hearing aid Directivity in small and reverberant enclosures using the root-mean-square amplitude of the first 3 ms of the hearing aid's response to the input signal. DESIGN: The hearing aid's planar DI and polar pattern were measured using the proposed method in an audiologic booth with low reverberation, a room with moderate reverberation, and an anechoic chamber. The measurement was repeated four times for each aid in each environment. The results were compared to the Directivity obtained in the anechoic chamber using two benchmark measurements. STUDY SAMPLE: Eight hearing aids with a fixed directional mode were tested. RESULTS AND CONCLUSIONS: The results revealed that the error of the proposed method in DI was smaller than 0.3 dB in 94% of the measurement conditions. The standard deviation of the DI was smaller than 0.1 dB in 94% of the conditions. These results suggest that the proposed quasi-anechoic method provides an accurate and repeatable way to assess non-adaptive directional microphone hearing aids in small non-anechoic enclosures.

  • predictive measures of directional benefit part 1 estimating the Directivity Index on a manikin
    Ear and Hearing, 2007
    Co-Authors: Andrew Dittberner, Ruth A. Bentler
    Abstract:

    OBJECTIVE: In this investigation, a method for computing a Directivity Index (DI) on a manikin for directional microphones in hearing aids was proposed and evaluated comparatively to other conventional methods. DESIGN: Test devices included first- and second-order directional microphones. Signal presentation, implemented in an anechoic chamber, involved a single noise source rotated completely around the directional microphone in a hearing aid, in free field and on a manikin, at a defined radius. The area covered was equivalent to the approximate surface area of a sphere. It was anticipated that an equal angular resolution of 10 degrees (elevation and azimuth) would effectively estimate the DI of first-, second-, and higher-order directional microphone systems located in a hearing aid on a manikin. A total of 450 spatially varied presentation points were analyzed, each weighted in reference to direction of arrival on the directional microphone. RESULTS: Empiric differences between the DI derived from the 3D-DI method proposed in this investigation and the conventionally derived 2D-DI method DI on a manikin were as large as 3.8 dB in the higher frequencies, depending on the device under test. CONCLUSIONS: The magnitude of these differences was dependent on the device under test microphone location. The further the microphone was placed into the ear of the manikin, the larger the empiric differences.

  • method for calculating Directivity Index of a directional microphone in a hearing aid on a manikin
    Journal of the Acoustical Society of America, 2005
    Co-Authors: Andrew Dittberner, Ruth A. Bentler
    Abstract:

    A method for computing a Directivity Index (DI) on a manikin for directional microphones in hearing aids is proposed and investigated. Test devices included first‐ and second‐order directional microphones in hearing aids. Signal presentation involved a single noise source rotated completely around the directional microphone, in free field and on a manikin, at a defined radius. The area covered was equivalent to the approximate surface area of a sphere. It was anticipated that an equal angular resolution of 10 deg (elevation and azimuth) would effectively estimate the DI of first‐, second‐, and higher‐order directional microphone systems located in a hearing aid on a manikin. A total of 450 spatially varied presentation points was analyzed, each weighted in reference to direction of arrival on the directional microphone. The absolute difference between the Directivity Index derived from the modified method proposed in this investigation and the conventionally derived Directivity Index on a manikin were as ...

  • verification of the Directivity Index and other measures of Directivity in predicting directional benefit
    Journal of the Acoustical Society of America, 2005
    Co-Authors: Andrew Dittberner, Ruth A. Bentler
    Abstract:

    The relationship between various Directivity measures and subject performance with directional microphone hearing aids was determined. Test devices included first‐ and second‐order directional microphones. Recordings of sentences and noise (Hearing in Noise Test, HINT) were made through each test device in simple, complex, and anisotropic background noise conditions. Twenty‐six subjects, with normal hearing, were administered the HINT test recordings, and directional benefit was computed. These measures were correlated to theoretical, free‐field, and KEMAR DI values, as well as front‐to‐back ratios, in situ SNRs, and a newly proposed Db‐SNR, wherein a predictive value of the SNR improvement is calculated as a function of the noise source incidence. The different predictive scores showed high correlation to the measured directional benefit scores in the complex (diffuse‐like) background noise condition (r=0.89−0.97, p<0.05) but not across all background noise conditions (r=0.45−0.97, p<0.05). The Db‐SNR ap...