摘要:

It is widely held that certain parts of the auditory spectrum are more important than others for speech recognition. However, the concept of frequency importance for speech recognition has received relatively little attention from researchers over the years. This was probably because most assumed that published frequency importance functions for nonsense syllables were satisfactory for most applications. Recent research suggests that different types of speech materials have different importance functions and that predictions of speech recognition for one speech material cannot be made accurately under all conditions using an importance function for a different material. Research on this topic will be reviewed and some recent data presented. An important remaining question is the effect that size of the frequency importance function has under different listening conditions. Early findings suggest that, although the importance function has relatively little influence on outcomes under some conditions, it can be substantial in others.

ISSN:0001-4966    

DOI:10.1121/1.2028955

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Intelligibility‐weighted, averaged gain [P. M. Peterson, “Adaptive array processing for multiple microphone hearing aids,” MIT (1989)],GI, has been used as a figure of merit to evaluate adaptive spatial filtering algorithms for noise cancellation hearing aids.GIis computed from the input and output signal and noise power spectra. An estimate ofGI,GI(w), can also be computed from the instantaneous directional frequency response of the adaptive spatial filter.GI(w) andGIare equivalent when the input signal and noise spectra are identical and the sound‐field nonreverberant; however, their relationship for other signal and noise spectra is unknown. SinceGI(w) is computed by the filter coefficients, it can potentially be used as a criterion for design of spatial filtering algorithms that maximize intelligibility rather than signal/noise ratio. Studies were conducted to evaluateGI(w) as a predictor of intelligibility by comparingGI(w) withGI(w), AI, and actual measured intelligibility and sound quality. The two‐sensor Griffiths‐Jim beamformer with speech and noise inputs processed by a reverberant room simulation to produce the evaluation materials is used. The results of these evaluations will be presented, and the validity of these measures for use in the design of noise cancellation hearing aids will be discussed.

ISSN:0001-4966    

DOI:10.1121/1.2028960

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Teleost fishes can vocalize by contracting striated muscles attached to the lateral walls of their swimbladder. The rhythmic, oscillatory‐like, firing properties of a brain‐stem sonic motor circuit determine the fundamental frequency of the acoustic signals. In the midshipmanPorichthys notatusonly large, nest‐building, egg‐guarding males generate long duration (up to 1 h) “hums” that attract females to the nests. Females, and smaller, “sneak‐spawning” males, do not hum. Behavorial sex differences in sound production are correlated with: (a) the soma‐dendritic dimensions and discharge frequency of individual sonic motoneurons and their presynaptic pacemaker neurons, (b) the functional architecture of sonic muscle fibers and myofibrils, and (c) the density of neuromodulator inputs to the sonic motor nucleus. The sonic motor circuit can serve as a “simple” model system for a detailed analysis of the synaptic and electro‐responsive properties of single neurons controlling the generation of sex‐ and species‐typical acoustic communication signals. The collaboration of Harriet Baker, Robert Baker, Richard Brantley, and Margaret Marchaterre is acknowledged. [Work supported by NSF, NIH, and Hatch Grants.]

ISSN:0001-4966    

DOI:10.1121/1.2028964

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

The African electric fishPollimyrus isidori(Mormyridae) is distinguished among sound‐producing fish by a relatively elaborate repertoire of temporally patterned sounds, produced by males while courting females. Courtship occurs in darkness, and the male's sonic display is evoked by the particular pattern of electrical discharges the female emits. Courtship communication thus involves a bimodal exchange of information mediated by both the auditory and electrosensory systems. Anatomically, these fish exhibit a peripheral specialization for underwater sound‐pressure transduction consisting of the attachment of the sacculus to the wall of a small gas‐filled bladder within the labyrinth. Single‐unit neuro‐physiology has been used to examine responses to sounds propagated through water and to examine the representation of temporally patterned sounds in the central nervous system. ThePollimyrusauditory system is quite sensitive to sounds in the frequency range of those used in communication, with some midbrain neurons having thesholds more than 60 dB below the pressure levels recorded close to sound‐producing males (thresholds of −30 dB or less,re: 1.0 dyn/cm2). The auditory midbrain shows a number of properties expected of a system involved in processing communication and other low‐frequency, temporally patterned sounds. [Work supported by NIH: NRSA DC00020‐02 and CDR P50 DC00293‐06.]

ISSN:0001-4966    

DOI:10.1121/1.2028969

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Traditionally, swimbladders of fish have been modeled in two regions. In the acoustic long wavelength region, i.e., λ much larger than the dimensions of the swimbladder, the gas‐filled bubble has been used. Since a spherical bubble has a very sharp resonance, damping terms have been included to broaden the resonance peak. The spherical bubble has been stretched into a prolate spheroid without reformulating the bubble theory [M. Strasberg, L Acoust. Soc. Am.25, 536‐537 (1953) and R. H. Love, J. Acoust. Soc. Am.64, 571‐580 (1978)]. At short wavelengths compared to the dimensions of the swimbladder, the scattering process depends on the shape of the swimbladder. Experimental and theoretical studies of the sound scattered by swimbladders include measurements of fish and numerical integrations of the Kirchhoff diffraction integral. The Kirchhoff approximations give “good” approximations to the backscattering cross sections at short wavelengths [K. G. Foote, J. Acoust. Soc. Am.78, 688‐700 (1985) and M. A. Do and A.M. Surti, J. Acoust. Soc. Am.87, 1588‐1596 (1990)]. For a single model, a finite gas‐filled cylinder can be used over the whole frequency range. Stanton's approximation for the finite fluid cylinder was used and the fluid used was a gas [T. S. Stanton, J. Acoust. Soc. Am.83, 55‐63 (1988)]. It will be shown that the gas‐filled cylinder model fits a well‐documented set of data [D. V. Holliday, J. Acoust. Soc. Am.51, 1322‐1332 (1972)]. [Work supported by ONR.]

ISSN:0001-4966    

DOI:10.1121/1.2028971

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

The effects of simultaneous exposures to whole‐body vibration and steady‐state noise were observed for thresholds of hearing in chinchillas. Four groups of animals were exposed to one of the following conditions: (a) noise only (500 Hz centered octave band, 100 dB SPL); (b) vibration alone at body resonance (63–89 Hz, 0.1grms, 1.0grms); (c) noise + resonant vibration; and (d) noise + nonresonant vibration (14–20 Hz, 0.1grms, 1.0grms,). The exposures lasted 6 h per day over 20 consecutive days. No interaction was demonstrated with the combination of nonresonant vibration and noise, but small increases in TTS and PTS were observed when the resonant vibration was added to the noise. Increasing the acceleration from 0.1grmsto 1.0grmsdid not result in a corresponding increase in TTS. Thresholds in the group exposed only to vibration improved slightly.

ISSN:0001-4966    

DOI:10.1121/1.2028975

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

During the past few years there has been an increasing interest in applying higher‐order spectra (statistics) to a wide range of signal processing and system theory problems. These statistics are very useful in problems where either non‐Gaussianity, nonminimum phase, colored noise, or nonlinearities are important and must be accounted for. When signals are random processes, then cumulants are used as the higher‐order statistics. When they are nonrandom, then moments are used. New methods have been developed that work either in cumulant or moment domains; in their multidimensional Fourier transform (i.e., “polyspectral”) domains; or, even in inverse logarithmic (e.g., high‐order “cepstral”) domains. Applications of higher‐order spectra to acoustics problems include transient signal reconstruction based on moving average, autoregressive, or autoregressive moving average models, when measurements are colored and Gaussian; detection of transient signals (in additive colored Gaussian noise); time delay estimation when measurement noises are correlated but Gaussian; and harmonic retrieval.

ISSN:0001-4966    

DOI:10.1121/1.2028978

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

The behavior of an acoustical system may be represented using either a transfer function or impulse response. This representation enables an electrical model of the acoustical system to be created. The output of this model may be used to drive an acoustical source and produce a secondary wave to cancel an undesired primary wave. A system identification process generates the required model using an adaptive parameter estimation scheme. A variety of alternatives are available for the model structure as well as the parameter estimation scheme. These include a finite impulse response (FIR) or infinite impulse response (IIR) digital filter with parameters obtained using a least‐mean‐square (LMS) or recursive least‐mean‐square (RLMS) adaptive algorithm, respectively. Since the process is one of adaptive control, the filtered‐Xor filtered‐Ualgorithm can be used to compensate for various transfer functions, identified on an off‐line or on‐line basis, following the adaptive model. Results will be presented from a variety of applications of this technology.

ISSN:0001-4966    

DOI:10.1121/1.2028980

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

A sound cancellation system has been developed to reduce the flow‐induced noise in piping systems under both steady‐state and transient conditions. A hybrid controller that combines both open‐loop and closed‐loop responses with adaptive digital signal processing and filtering techniques is utilized to speed up the response of the system controller for the transient condition. Autoregressive, moving average with exogenous input (ARMAX) alogrithm has been utilized in the on‐line and off‐line modeling of signal characteristics. Off‐line model data are introduced into an on‐line adaptive system model via a parameter leakage mechanism. The convergence of the resulting algorithm is improved at the expense of bias in the final system parameters. The bias depends on a weighting or leakage factor, which controls the relative amount of off‐line data to be used. A preliminary test has been conducted to demonstrate the active cancellation concept for synthesized steady‐state signals. Results showed that up to a 30‐dB reduction has been obtained for pure sinusoidal waves ranging from 100 to 500 Hz. For confined jet noise, the noise reduction is about 10 dB, and similar results have been observed for the random broad‐band noise.

ISSN:0001-4966    

DOI:10.1121/1.2028987

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

In ordinary daily experience, the forces associated with sound waves are usually negligible. In a resonator, the sound levels can be much greater and hence the Bernoulli forces can create a variety of dramatic effects. This video will illustrate the pressure and velocity fields in a standing wave tube using a microphone and hot‐wire anemometer. This standing wave field will then be used to demonstrate the “Maidenform effect” and acoustic levitation. Radiation pressure will be demonstrated using a Helmholtz resonator and then a pair of Helmholtz resonators will be used to make an acoustic radiometer. The standing wave field will then be extended from one to two dimensions to illustrate the torque on a Rayleigh disk and, finally, the controlled rotation of objects in a standing wave field whose particle motion is determined by the relative phasing of the degenerate modes. [Work supported in part by the Naval Postgraduate School Direct Funded Research Program.]

ISSN:0001-4966    

DOI:10.1121/1.2028991

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP