摘要:

Binaural, free‐field, speech‐reception thresholds (SRTs) in 70‐dBA noise were measured with conversational sentences for 24 hearing‐impaired subjects without a hearing aid, with a hearing aid at the right or at the left ear, and with two hearing aids. The sentences were presented in front of the listeners and interfering noise was presented either frontally or laterally. Subjects used their own binaural behind‐the‐ear hearing aids and adjusted the gain(s) for optimum intelligibility in 70‐dBA noise. Subjects had nearly symmetrical hearing losses with an average over 500, 1000, and 2000 Hz of between 30 and 65 dB. For hearing losses below 50 dB the SRT in both ears was determined by the S/N ratio even when only one hearing aid is used with the unaided ear at the shadow side of the head. It appears that, just as for monaural hearing aids, a second hearing aid generally does not improve the SRT under conditions with a high noise level. However, for situations with a low noise level or a high absolute threshold, in which a monaural hearing aid is profitable, a binaural aid is even more profitable.

ISSN:0001-4966    

DOI:10.1121/1.2021945

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

A three‐phase assessment paradigm was implemented to identify possible areas of dysfunction in auditory visual perception and processing by mathematically impaired subjects. Phase I involved assessing peripheral auditory acuity, Phase II tested central auditory processing, and Phase III evaluated cortical integration of auditory and visual sensory information. Several diagnostically significant profiles emerged from the test data, and will be discussed in regard to relevance in designing successful mathematical training programs for the mathematically impaired population. The profiles will be presented and discussed as to clinical and educational repercussions.

ISSN:0001-4966    

DOI:10.1121/1.2021950

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Sound absorption in sea water involves chemical equilibria with rather slow relaxation rates. The low‐frequency range of the resonator method is limited by practical considerations of size and experimental conditions must usually be altered to place the relaxation frequency within the measurement window. For relaxations involving acids or bases, the temperature‐jumppH method permits rate measurements below a limit set by indicator response (∼ 105/s). RecentT‐jump studies confirm unambiguously that the low‐frequency (∼ 1 kHz) relaxation mechanism in sea water is an acid‐base exchange between boric acid and carbonate [P. Malloet al., J. Phys. Chem. (in press) (1984)]. Further investigations of the boric acid exchange in similar Lewis systems, e.g., ammonia, reveal single relaxations with comparable rates. The magnesium carbonate ion‐pair equilibrium—a minor component of sea water absorption at mid‐frequencies (∼ 10 kHz)—shows more complex behavior with several identifiable relaxations in the measurement range. The magnesium sulfate relaxation (∼ 100 kHz) is unsuited to the method because of both speed and lack ofpH dependence. Visiting scientist; home address: 117 Boston Post Road, Old Lyme, CT 06320.

ISSN:0001-4966    

DOI:10.1121/1.2021957

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Previously, we presented [L. H. Greenet al., J. Acoust. Soc. Am. Suppl. 175,S77 (1984)] an analysis of the low‐frequency high‐Qresonances of thin spherical shells. The previous investigation centered on providing a physical explanation for the strong coupling of the lowest frequency resonances to the fluid medium. We extend the analysis to more completely explore the effects of fluid loading on the high‐Qresonances. In particular, as the phase velocity of the low speed (first mode) wave on a thin spherical shell approaches the speed of sound in the fluid, the dispersion curve for the elastic wave appears to merge with that of the “creeping wave.” A physical explanation of this effect will be provided along with numerical results based on the linear theory of elasticity.

ISSN:0001-4966    

DOI:10.1121/1.2021963

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

A finite element analysis solution for the normal modes in a rectangular room characterized by a small patch of highly absorptive material on one wall was performed. The authors' previous results for this problem indicated a nonphysical falloff of the sound intensity near the source [J. Acoust. Soc. Am. Suppl. 174,S23 (1983)]. The reason for this falloff has been identified as a result of the truncation of the Green's function eigenvalue expansion required by the finite element method. This paper shows that this behavior can be overcome (to a large extent) by performing certain algebraic manipulations on the form of the Green's function prior to truncation. The result is an improved rate of convergence of the Green's function, particularly near the source. A more accurate analysis of the energy flow can then be obtained with a limited number of low‐frequency modes. Results obtained with this new approach will be compared with those found in the authors previous work.

ISSN:0001-4966    

DOI:10.1121/1.2021971

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Recent work by the author has included two computation‐intensive models that suffer severe practical limitations if forced to run on commonly available computers such as a DEC VAX 11/780. Results of one of the models PERUSE were recently published [J. Acoust. Soc. Am.75,1415 (1984)]. The second model is a state‐of‐the‐art coupled mode model described by C. A. Boyles [J. Acoust. Soc. Am.73,800 (1983)] and implemented numerically by the author [J. Acoust. Soc. Am. Suppl. 173,S96 (1983)]. Results of both models will be presented and discussed in light of how computation time relates to the complexity of the particular problem being solved. Citing also earlier work by the author and F. D. Tappert [J. Acoust. Soc. Am.63,353 and 533 (1978)] involving expensive Monte Carlo calculations required to verify a theory of stochastic wave propagation, a forceful argument will be made that solutions to some of the most pressing problems on the frontier of ocean acoustics today require the use of supercomputers or dedicated array processors.

ISSN:0001-4966    

DOI:10.1121/1.2021973

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Acoustic scattering from surfaces with high slope elements is modeled numerically by describing the surface as a conjoint assemblage of wedges. The impulse response of the surface is then obtained by adding the single wedge responses which are calculated from the Biot and Tolstoy solution [J. Acoust. Soc. Am.29,381–391 (1957)]. By use of the FFT the spectral description of the scattered field is obtained. This method is then applied to the study of mode interaction due to wall roughness in waveguide propagation [Research supported by ONR.]

ISSN:0001-4966    

DOI:10.1121/1.2021978

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

When an explosive charge is detonated under water, the explosion produces a shock wave and an oscillating gaseous bubble whose behavior is intimately related to the physical properties of the explosive itself and of its environment. Many of these properties can be calculated from detailed measurements of the shock wave and of the bubble and its oscillations, but such measurements are seldom available for large explosions. We show an iterative inversion procedure for making band‐limited estimates of the shock wave and bubble oscillation pressure waveforms from power spectra of farfield hydroacoustic recordings of large underwater explosions. We also show the ensemble averaging procedure that is needed to produce spectral estimates of sufficient stability and resolution to support the inversion procedure.

ISSN:0001-4966    

DOI:10.1121/1.2021981

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Noise source identification in turbomachinery often requires estimation of the correlation between multiple rotating (aerodynamic) sources and the stationary radiated sound field. When treated as a multiple input/output problem, relative motion between input (sources) and output signals has the effect of amplitude and phase, modulating the input. The resulting nonlinearities introduced into the system affect the estimation of the coherence function. A straightforward approach will be used to examine the AM and PM effects as they pertain to the multiple input/output model for rotating sources. As pointed out in the literature on rotating diffuser models [Elko, M.S. thesis, Pennsylvania State University (1980)], source directivity plays a significant role in determining the strength of the AM spectra. This point is best illustrated by comparing the results of rotating monopoles and dipoles, and extrapolating these results to other radiation patterns. The consequences of PM are viewed through the general Doppler formula, applied to the specific geometry of rotating sources in an arbitrary plane with respect to a fixed observer. The possibility of removing the AM/PM effects by prepossessing the signals will also be discussed.

ISSN:0001-4966    

DOI:10.1121/1.2021990

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Annoyance reactions caused by exposure to noise consisting of clearly defined noise events in a steady background have been studied. The noise resembled that of heavy vehicles passing at a short distance or aircraft flyover near an airport. With all other parameters kept constant, the annoyance experienced by the test subjects seems to be highly dependent on the time between each single noise event. Interevent intervals of the order of 2 to 5 rain seem to be the least annoying. The results from this experiment have been combined with a previously published threshold theory to make a new model for assessing the annoyance caused by typical community noise.

ISSN:0001-4966    

DOI:10.1121/1.2021994

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP