摘要:

Frequency resolution was evaluated for two normal‐hearing and seven hearing‐impaired subjects with moderate, flat sensorineural hearing loss by measuring percent correct detection of a 2000‐Hz tone as the width of a notch in band‐reject noise increased. The level of the tone was fixed for each subject at a criterion performance level in broadband noise. Discrimination of synthetic speech syllables that differed in spectral content in the 2000‐Hz region was evaluated as a function of the notch width in the same band‐reject noise. Recognition of natural speech consonant/vowel syllables in quiet was also tested; results were analyzed for percent correct performance and relative information transmitted for voicing and place features. In the hearing‐impaired subjects, frequency resolution at 2000 Hz was significantly correlated with the discrimination of synthetic speech information in the 2000‐Hz region and was not related to the recognition of natural speech nonsense syllables unless (a) the speech stimuli contained the vowel /i/ rather than /a/, and (b) the score reflected information transmitted for place of articulation rather than percent correct.

ISSN:0001-4966    

DOI:10.1121/1.395285

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

Frequency discrimination of spectral envelopes of complex stimuli, frequency selectivity measured with psychophysical tuning curves, and speech perception were determined in hearing‐impaired subjects each having a relatively flat, sensory‐neural loss. Both the frequency discrimination and speech perception measures were obtained in quiet and noise. Most of these subjects showed abnormal susceptibility to ambient noise with regard to speech perception. Frequency discrimination in quiet and frequency selectivity did not correlate significantly. At low signal‐to‐noise ratios, frequency discrimination correlated significantly with frequency selectivity. Speech perception in noise correlated significantly with frequency selectivity and with frequency discrimination at low signal‐to‐noise ratios. The frequency discrimination data are discussed in terms of an excitation‐pattern model. However, they neither support nor refute the model.

ISSN:0001-4966    

DOI:10.1121/1.395286

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

Sequences of rapidly occurring sounds that differ from each other are often perceptually segregated into ‘‘streams’’ within which the range of differences is smaller [Bregman and Campbell, J. Exp. Psychol.89, 244–249 (1971)]. Early research on streaming implied it to be pitch dominated, but Wessel [Comput. Music J.3, 45–52 (1979)] demonstrated that timbre differences could also bring about segregation. In the present study, pitch and timbre attributes were put in competition in four‐tone sequences of the form:T2P1‐TmP1‐T2Pn‐TmPn, with the first pair assigned pitchP1but different timbresT2andTm, and the second pair pitchPn, and similarly contrasted timbres. Six listeners were asked to indicate whether perceived grouping of 49 such sequences was based on pitch proximity, timbre similarity, or ambiguous percepts not dominated by either cue. Results confirm that timbre can segregate sequences and imply that timbre and pitch compete in perceptually organizing complex sequences. Because timbre differences were provided by varying the locus of four equal‐amplitude harmonics, and pitch differences were provided by varying their relative spacing, it is suggested that the tradeoffs observed may actually arise due to differences in perceived salience of ‘‘spectral pitch’’ and ‘‘virtual pitch’’ [Terhardt, J. Acoust. Soc. Am.55, 1061–1069 (1974)] dependent on relative changes in spectral locus and spectral spacing over time.

ISSN:0001-4966    

DOI:10.1121/1.395287

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

The purpose of this research was to determine if infants, like adults, show differential localization performance in the median sagittal plane (MSP) as a function of the spectrum of the signal. Infants 6–18 months of age were seated in a dark room facing an array of nine loudspeakers, with one loudspeaker positioned at ear level, 0°, and four each positioned above and below ear level at 4°, 8°, 12°, and 16°. A two‐alternative, forced‐choice procedure was used in which a sequence of noise bursts was presented at 0° and then shifted vertically, above or below 0°, and continued to be presented until the infant made a directional head and/or eye movement; correct responses were visually reinforced. For each of three bandpass noise conditions (<4 kHz, 4–8 kHz, 8–12 kHz), minimum audible angle (MAA) for each listener, i.e., the smallest of the four angular shifts in vertical sound location that the listener could reliably detect, was estimated. Results indicated that MAA systematically decreased with increasing age, revealing an increasingly finer partitioning of auditory space. Moreover, performance at each age revealed the importance of high frequencies for localization in the MSP. Infants did not reliably localize the low‐pass signal (<4 kHz) and showed the best performance to the signal comprising the highest frequencies (8–12 kHz). These findings reveal systematic age‐related improvements in sound localization abilities during infancy, and suggest that spectral cues similar to those for adults operate for infants in vertical localization.

ISSN:0001-4966    

DOI:10.1121/1.395288

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

Devices that convert sound patterns into patterns of vibrotactile stimulation have been shown in laboratory and clinical studies to enable persons to appreciate many aspects of the acoustic environment, and thus are of potential benefit to deaf persons. In the present article, a framework is outlined for describing normal listening situations as a hierarchy of tasks requiring increasingly complex analysis of the acoustic waveform, including sound detection, environmental sound identification, syllable rhythm and stress categorization, phoneme and word identification, and comprehension of connected speech. The types of benefits provided by tactile aids in each of these tasks are exemplified using data from studies of single‐channel commercially available devices and multichannel tactile vocoders in our own and other laboratories. The discussion of these data addresses such issues as the features of the acoustic environment that can or should be transmitted through a tactile aid, the differences in the information transmitted by commercially available versus experimental laboratory devices, the comparison of tactile aids and cochlear implants, and the technical problems that remain to be overcome in the design and evaluation of improved vibrotactile aids.

ISSN:0001-4966    

DOI:10.1121/1.395289

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

The question of whether one can conclude just from basilar membrane (BM) vibration data that the cochlea is an active mechanical system is addressed. To this end, a method is developed which computes the power flux through a channel cross section of a short‐wave cochlear model from a given BM vibration pattern. The power flux is an important indicator of mechanical activity because a rise in this function corresponds to creation of mechanical energy. The power flux method is applied to BM velocity patterns as measured by Johnstone and Yates [J. Acoust. Soc. Am.55, 584–587 (1974)] and by Sellicketal. [Hear. Res.10, 101–108 (1983)] in the guinea pig and by Roblesetal. [PeripheralAuditoryMechanisms, edited by J. B. Allen, J. L. Hall, A. E. Hubbard, S. T. Neely, and A. Tubis (Springer, New York, 1986a), pp. 121–128, and J. Acoust. Soc. Am.80, 1364–1374 (1986b)] in the chinchilla. Before the calculations are performed, the BM data are interpolated and smoothed in order to avoid numerical errors as a result of too few and noisy data points. The choice of the smoothing method influences the computed power flux function considerably. Nevertheless, the calculations appear to make a clear distinction between the ‘‘old’’ data, showing broad BM tuning (Johnstone and Yates, 1974), and the ‘‘new’’ data, in which the response is much more peaked (Sellicketal., 1983; Roblesetal., 1986a,b). The former do not give rise to a significant increase of the power flux; the latter do, although less convincingly for the Sellicketal. (1983) data than for the Roblesetal. (1986a,b) data. It is thus concluded that the recently obtained, sharply tuned BM responses reflect the presence of mechanical activity in the cochlea.

ISSN:0001-4966    

DOI:10.1121/1.395290

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

A discrete layered absorbing acoustic medium is probed with an impulsive plane wave at normal incidence, and the reflection response of the medium is measured. The absorbing nature of the medium is specified by a complex wave speed, corresponding to a constantQ. A fast layer stripping algorithm for recovering the profile of the complex wave speed as a function of depth is obtained. The algorithm works by recursively computing the reflection response of that portion of the medium below the current depth, thus stripping away the effects of that portion of the medium at and above the current depth. The algorithm is, in principle, exact, includes the effects of multiple reflections, and admits a clear physical interpretation of its operation. Several computer simulations illustrate the performance of the algorithm on synthetic data.

ISSN:0001-4966    

DOI:10.1121/1.395291

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

In this article, the transient sound radiation from a clamped circular plate with a viscoelastic layer excited by impact is studied analytically and experimentally. The composite plate vibrations are obtained by using the normal mode analysis and the eigenvalues are obtained by a Mindlin plate theory, including the rotary inertia and shear deformation. In impact, the contact force developed between the ball and the plate with attached layers is obtained by Hertz contact theory. The radiated sound pressure in the farfield is calculated by the Rayleigh integral. Prediction of the waveforms of sound radiating from the plate with attached layers and a method for reducing noise generation from the plate by impact force are also shown in this article. The analytical results can be applicable to multilayered plate and noncentral impacted cases. Using the results of this article, the thickness of an attached viscoelastic layer to reduce the noise to the desired level can be decided.

ISSN:0001-4966    

DOI:10.1121/1.395292

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

This article is concerned with the parametric instability of circular plates elastically restrained against translation and rotation at concentric intermediate circles as well as along the periphery. The plate is subjected to a horizontal or tangential periodic radial load at the periphery. The instability regions of the plate both for the simple resonance and for the combination resonances of sum and difference types are determined analytically from the coupled Mathieu equations that are derived by applying the Galerkin method to the governing equations. The influences on the stability of the plate of the direction of periodic load and the stiffness of elastic supports are studied in detail for the plate with peripheral and one intermediate supports.

ISSN:0001-4966    

DOI:10.1121/1.395293

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

The wave propagation in a piezoelectric hollow cylinder of class (6‐mm) crystals or ceramics (∞ m) with traction‐free surfaces is studied. The frequency equations are obtained subject to various types of electrical boundary conditions and are examined numerically for the piezoceramic material PZT‐4; the results are presented graphically as well as in tables.

ISSN:0001-4966    

DOI:10.1121/1.395294

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP