摘要:

Computational models of the peripheral auditory system have largely modeled basilar membrane (BM) mechanics as a linear filter-bank-like entity. Recent mathematical work on the nature of auditory system noise suppression allows us to analyze and argue for the incorporation of BM nonlinearities into these models. This analysis shows that vowel perception improves with increasing presence of BM nonlinearities whereas consonant perception degrades with increasing influence of BM nonlinearities. Experimental results on tones and real speech corrupted by noise corroborate the analysis as well as suggest a novel approach to speech processing.

ISSN:0001-4966    

DOI:10.1121/1.422789

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

An envelope-based method to estimate both the jet-wave amplification factor and the mouth-field strength in organ pipes is developed by using flow visualization of a smoked jet with a high-speed digital video camera. A theoretical envelope of wave growth, which is approximated using a negative displacement model of the jet drive, is compared with an experimental envelope derived from superposing many instantaneous shapes of jet deflection in the steady-state oscillation. The estimation results are presented in dimensional terms with respect to two particular models, where the flue-to-edge distances are, respectively, 15.8 and 10.2 mm, with a common flue thickness of 2.2 mm. In our experiment the jet velocity ranges from 7 to 33 m/s, the Reynolds number from 1000 to 5000, and the sounding frequency from 130 to 580 Hz. The amplification factor of organ pipe jets, estimated to lie in the0.18–0.26-mm−1range, tends to decrease and saturate with increasing blowing velocity in each oscillation mode; the mouth-field strength defined as the acoustic displacement amplitude, roughly estimated to be 0.5–1.5 mm, tends to increase and saturate with increasing blowing velocity. A hot-wire anemometer is then used to measure the mouth-field strength, whose value shows a good agreement with the estimated one. This result confirms the validity of our envelope-based method. A dimensionless representation of the experimental data is used to compare wave characteristics between an organ pipe jet and an acoustically perturbed free jet. The applicability of the spatial and temporal theories of jet instability is discussed to analyze them. If we can assume a Poiseuille flow at the flue exit and a subsequent Bickley jet, the spatial theory seems to be relevant to our organ pipe jets. However, for lack of a reliable experimental measurement of the jet half-thickness we cannot draw a definite conclusion about the wave characteristics of organ pipe jets.

ISSN:0001-4966    

DOI:10.1121/1.423113

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

This paper presents the experimental results on the acoustic anisotropy in bovine cancellous bone. The propagation of both fast and slow longitudinal waves in bovine cancellous bone was experimentally examined in relation to the structural anisotropy, or the trabecular arrangement. Propagation speeds of the fast and slow waves were measured as a function of the propagation angle to the trabecular alignment, and theoretically estimated by use of Biot’s theory for an isotropic medium.

ISSN:0001-4966    

DOI:10.1121/1.422790

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Input parameters to the Biot theory, used by N. P. Chotiros [J. Acoust. Soc. Am.97, 199–214 (1995)] in an effort to claim that a slow wave propagating at 1200 m/s was experimentally observed in near-bottom sand, are shown to be inconsistent with generally accepted results from prior theoretical and experimental studies of granular media.

ISSN:0001-4966    

DOI:10.1121/1.422791

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The approach advocated by Prof. Stoll, which lead to the parameter values marked “Historical,” has worked well for porous materials with cemented frames, such as fused glass beads and sandstone, but it does not work for sand. The parameter values, marked “Chotiros,” are uniquely able to match all four. The main issue lies with the values of the frame and grain moduli.

ISSN:0001-4966    

DOI:10.1121/1.422792

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

A modal model, initially developed to modelize diffraction of electromagnetic waves by rectangular-groove gratings, is used to describe ultrasonic surface waves above the same structures in air. A simple analytical formulation which provides results comparable to the modal method is presented. Measurements performed on ultrasonic surface waves are compared to predictions obtained with the simplified formulation and the modal model.

ISSN:0001-4966    

DOI:10.1121/1.422793

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The recent paper by [J. Acoust. Soc. Am.101, 950–963 (1997)] uses as a primary outcome measure an estimate of hearing handicap based on a weighted average of pure tone thresholds at 1, 2, 3, and 4 kHz. This choice is unusual and inadequately justified. If four equally weighted frequencies are to be chosen, the ANSI standard referenced by Prince et al. would suggest 0.5, 1, 2, and 4 kHz. If 1, 2, 3, and 4 kHz are chosen, the weights from ANSI 3.5, 1969 would be very different from those used by Prince et al.

ISSN:0001-4966    

DOI:10.1121/1.422794

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Concern is raised by Dobie [J. Acoust. Soc. Am.103, 2734 (1998)] regarding a recent analysis [, J. Acoust. Soc. Am.101, 950–963 (1997)] of the NIOSH Occupational Noise and Hearing Survey data. Specifically, issues are raised concerning (1) definition of hearing handicap, (2) the use of frequency-specific articulation index (AI) weights applied to the binaural pure-tone average of 1, 2, 3, and 4 kHz, and (3) conclusions regarding significant excess risk based on this definition. We have reviewed the development of the definitions of hearing handicap and provide additional support for the use of a hearing handicap definition based on the binaural pure-tone average of 1, 2, 3, and 4 kHz and the weighting of specific frequencies. Furthermore, our definition of noise-induced hearing handicap is similar to one of several proposed by the International Standards Organization (Reference 1999Reference 1990) and the American National Standards Institute (Reference 3Reference 44Reference 1996). Additional analyses show that there is significant evidence of excess risk at daily exposure levels below 85 dB using any of the pure-tone average and/or weighting strategies we have examined. Hence we have provided additional support for our conclusions regarding exposure-response curves and we have reaffirmed that our methods are appropriate for the scope of our analysis.

ISSN:0001-4966    

DOI:10.1121/1.422795

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

In small mammals, there is convincing evidence for the existence of two discrete components of distortion-product otoacoustic emissions (DPOAEs), which have been called, variously, the active, low-level, or peak component, and the passive, high-level, or basal component. However, in humans, there is no convincing evidence for the existence of two analogous components of the DPOAE, at least for stimulus levels up to 85 dB SPL. These differences indicate that caution is required when generalizing from models of DPOAEs in small mammals to the human situation.

ISSN:0001-4966    

DOI:10.1121/1.422796

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Speech processing technologies, including speech recognition, synthesis, and coding are expected to play important roles in an advanced multimedia society with user‐friendly human–machine interfaces. Speech recognition systems include not only those that recognize messages but also those that recognize the identity of the speaker. This paper predicts future directions in speech processing. It describes the most important research problems and tries to forecast where progress will be made in the near future and what applications will become commonplace as a result of the increased capabilities. The most promising application area is telecommunications. To solve various fundamental problems, a unified approach across speech recognition, synthesis, and coding is indispensable. Handling the common phenomenon of voice individuality from different aspects are: research on speaker adaptation in speech recognition, automatic speaker verification, voice conversion in speech synthesis, and the problems of very low‐bit‐rate speech coding quality variation from speaker to speaker. The methods that essentially solve such problems should be based on a common mathematical model. Research on the mechanism of speech information processing in our human brains, that is, how meanings of speech are understood and how speech is produced, is also crucial for epoch‐making technological development in conversational speech understanding and natural speech synthesis.

ISSN:0001-4966    

DOI:10.1121/1.422797

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP