摘要:

Forward masking of a 1‐kHz, 20‐ms probe was examined using two temporally distinct 1‐kHz, 20‐ms maskers, separated by 6.5 ms. The interval between the second masker and the probe was the same as the interval between the first and second masker. Masking functions were obtained for each masker separately, and for varying levels of one masker with a fixed level of the other. The presence of the first masker at a fixed level raised the probe threshold over that obtained with the second masker alone: this elevation was approximately constant, independent of the level of the second masker. The results indicate that masking effects of the two maskers are not independent, i.e., the maskers interact. Several models of masker interaction are discussed.

ISSN:0001-4966    

DOI:10.1121/1.384745

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The frequency selectivity for formant peaks in a synthetic continuous vowel was measured on a nonlinear model for motion of the basilar membrane. In spite of the fact that the model becomes more broadly tuned at high levels, the formant peaks in the model response become more sharply defined. This effect is caused by nonlinear suppression of the response to frequencies between adjacent formant peaks.

ISSN:0001-4966    

DOI:10.1121/1.384746

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

An analysis is made of the low‐frequency behavior of a three‐dimensional hydroelastic model of the cochlea. In essence, the fluid motion is described using the linearized Navier–Stokes equations and the basilar membrane is modeled as an elastic plate. It is found that, for the lower frequencies, resonating frequencies are present and are approximately 4 Hz apart. The problem is solved and an analysis is made of the effects of the geometry on the motion of the wave. To conclude, an asymptotic formula is derived for the place of maximum amplitude and it is found to compare favorably with von Békésy’s experimental results.

ISSN:0001-4966    

DOI:10.1121/1.384747

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

A chronic implant of a thermocouple, on the round window membrane of the guinea pig cochlea, was used to determine the cochlear temperature in awake, anesthetized, and surgically dissected animals. The normal cochlear temperature was equal to the core (rectal) temperature of the guinea pig (38.5 °C) and, in the intact animal, exactly tracks changes in core temperature at least down to the 33 °C level tested here. Ventral surgery to expose the cochlea results in a decrease, to a low value of 31 °C, in cochlear temperature because of the removal of tissue mass overlying the auditory bulla. Effective use of a heating pad and blanket cover, over the body of the guinea pig, will regulate core temperature but the exposed cochlea will always have a lower value than either the temperature measured rectally or in the orophraynx.

ISSN:0001-4966    

DOI:10.1121/1.384748

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Red‐winged blackbirds and brown‐headed cowbirds were trained with operant conditioning techniques and food reinforcement to categorize complex song themes from both their own (conspecific) and from the other (alien) species’ vocal repertoire. Following training, songs were separated into initial and terminal portions and birds were retested for identification of the isolated song elements. Results revealed no species differences in identifying the ’’introductory note’’ portions of redwing and cowbird song; however, redwings were superior to cowbirds in identifying terminal redwing ’’trills,’’ while cowbirds were superior in identifying terminal cowbird ’’whistles.’’

ISSN:0001-4966    

DOI:10.1121/1.384749

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

This paper reviews the basis for new efficient data analysis procedures to solve multiple input/output problems. Practical iterative computational techniques are explained for obtaining conditioned spectral density functions, partial and multiple coherence functions, and other desired quantitites. Examples are given on how to identify different multiple correlated noise sources and how to determine their separate frequency response functions to any desired response point.

ISSN:0001-4966    

DOI:10.1121/1.384760

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

This paper describes the design and measured performance of a serial phase shift beamformer which uses a charge transfer device (CTD) for storing the element samples from a cylindrical array. By using a serial structure the amount of hardware needed for multiple beams can be reduced markedly from that needed in conventional parallel preformed beams. Since one beamformer produces all beams, the beams have the same spatial characteristics. To demonstrate the potential cost and space benefits of the new architecture, an experimental version was built and tested to confirm the operational characteristics. The array used for the test was an existing AN/WQS‐1 cylindrical array. The beam pattern of the CTD was measured in the ARL:UT test tank. As an aid to performance evaluation, a time delay beamformer was also housed in the AN/WQS‐1 cylinder. The beam patterns of the two show close agreement in main lobe and sidelobe structure.

ISSN:0001-4966    

DOI:10.1121/1.384761

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The correlation of sounds with behavior in groups of free‐ranging whales has been restricted by the difficulty of determining which animal made the sound. A real‐time device was designed and built to directionalize on the underwater sounds of Southern Right Whales,Eubalaenaaustralis. The device measures the phase difference between the signals from a two‐dimensional hydrophone array and calculates a bearing to the sound source. Results of field calibration tests demonstrated that the system could reliably directionalize on right whale sounds with a resolution of ±12° except for arrival bearings within 25° of the array’s axis.

ISSN:0001-4966    

DOI:10.1121/1.384762

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Beamforming is an integral part of most signal processing systems in active or passive sonars. The delays used to generate a beam are functions of the sound velocity, which depends on temperature, salinity, and pressure. There is a loss in array gain if the delays are incorrectly set. This will occur when the sound velocity in the water surrounding the hydrophones is different from the velocity that was used to set the delays. This paper makes two points: (1) fixed delay line sonars suffer a loss in gain when the true sound speed in the water is different from the velocity that is used to set the delays, and (2) there are signal processing techniques for two‐ or three‐dimensional arrays that yield source bearings that are independent of the true sound velocity. These techniques require variable time delays, which can be realized using digital processing.

ISSN:0001-4966    

DOI:10.1121/1.384763

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Images obtained using synthetic aperture sonar systems are often degraded by the effects of multiplicative and additive noises resulting from turbulence of the medium, random vibrations of the transmitter and receiver system, and various noise sources. In this paper, first, a unified evaluation of the effects of multiplicative and additive noises on the reconstructed image is proposed. In this method, the coefficient of variation of the image is used as the measure. Then, the correlation technique, which has been proposed in a previous paper to reduce the effects of turbulence, is evaluated using this measure. To show the plausibility of the theoretical discussions, several experimental results, which were obtained using a specially arranged synthetic aperture sonar system to evaluate the effects, are presented. The relation between the number of sampling points and the quality of reconstructed images is shown, and the effect of the correlation technique is examined under the condition that large turbulences of the medium exist. These results show the effectiveness of the proposed method.

ISSN:0001-4966    

DOI:10.1121/1.384764

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP