摘要:

To this day it is widely accepted that localization of sounds in auditory space is determined primarily by two cues, interaural differences in stimulus intensity and time of arrival. However, recent research forces us to appreciate the deficiencies of this point of view. It cannot, for example, explain localization in the median plane or localization with one ear, both of which are done with reasonable accuracy. Nor can it account for the fact that stimuli presented (over headphones) only with interaural differences, appear to originate from inside the listener's head. Acoustic measurements (ours and others) show that in addition to interaural time and intensity differences, stimuli in free space produce large direction‐dependent spectral cues, resulting from the acoustic filtering action of outer‐ear structures (pinnae, etc.). These cues are large, and occur in relatively low‐frequency regions (below 5 kHz), even when the source is moved a small amount in the horizontal plane. When stimuli are computer synthesized such that both the spectral and interaural difference cues are preserved, headphone presentation produces a nearly perfect simulation of free‐field listening. Results from several recent experiments conducted in our laboratory and elsewhere lead us to the conclusion that the filtering action of the outer ear is at least as important to our perception of auditory space as is the fact that we listen with two ears [Work supported by NSF.]

ISSN:0001-4966    

DOI:10.1121/1.2020274

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

At one time it was felt that interaural differences of time could affect the localization only of low frequencies. Psychoacoustic support for this view came from observations with sinusoidal stimuli that showed a total insensitivity to interaural delays in tones above about 1.5 kHz. In recent years, however, it has become increasingly clear that listeners can detect interaural delay in signals of high‐frequency content, as long as the spectrum is complex. For example, performance can be excellent when the signal is a high‐frequency carrier that has been modulated in amplitude. The purpose of this paper is to discuss functional differences between simple and complex sounds, with an eye toward development of a model of binaural interaction that accounts for the responses to both. Toward this end, special attention will be paid to stimulus factors that differentiate the two classes. In the preceding paper, Yost compares the responses to interaural differences of time in the stimulus onset and in the waveform. That notion will be expanded here in a model which attributes a spectral role to onsets and which visualizes both individual peaks in the envelopes of high frequencies and the oscillations of low frequencies as successions of mini‐onsets.

ISSN:0001-4966    

DOI:10.1121/1.2020322

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

This paper presents the second part of a report on the changes in intelligibility of synthetic speech produced by training. Two groups of subjects received training between the pre‐test and post‐test assessments of the intelligibility of the Votrax Type‐N‐Talk system. One group was explicitly trained on the synthetic speech. The second group received the same training procedures with natural speech. During training, subjects were presented with isolated words, meaningful and anomalous sentences, and prose passages. On each trial for words and sentences after identifying the stimulus, subjects were presented with feedback of a visual presentation of the stimulus and a second auditory presentation. For the first prose passage, subjects were given a printed version to read during auditory presentation of the passage. Subjects listened to three other passages without a printed version and then answered comprehension questions. Accuracy of word identification and response latency and accuracy to comprehension questions were recorded. Based on these data we will discuss the time‐course of learning to perceive synthetic speech more accurately.

ISSN:0001-4966    

DOI:10.1121/1.2020369

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Explanations of phonetic perception describe the conversion of the acoustic signal to phonetic segments. By making the descriptions of phonetically relevant patterns abstract, these explanations have accomodated the great variability evident in the acoustic signals produced by different talkers and in different utterances by the same talker. In order to refine this characterization of perception, we sought to determine the precise limits of phonetically useful information over frequency variation. A frequency transposition test was performed with three sentences, employing the technique of sinusoidal replication of natural utterances. This technique emphasized time‐varying acoustic information, and also controlled for timbre changes over frequency. The results show that a phonetic listening band may exist within the human range of audible frequencies. The relation of this finding to frequency coding, perception of musical pitch, and development of sensory prostheses will be discussed. [Supported by the National Institute of Child Health and Human Development.]

ISSN:0001-4966    

DOI:10.1121/1.2020421

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

SRS, Hertz's language‐independent synthesis rule development system, has been used recently to write a set of phoneme‐based rules for Japanese. This paper will describe the Japanese prosody rules, which operate on phonological phrases of various sizes to generate natural‐sounding prosodic patterns. The phrases are demarcated in the romanized input string by an easy‐to‐learn annotation scheme. The annotations are translated into boundary symbols and associated boundary features. These features, together with accent marks, are used to generate a segment‐by‐segment specification by prosody features, such as [low] (low‐pitched) and [ace](accented). Synthesizer parameter rules then refer either to the boundaries' features or to the intervening segments' features to produce various aspects of an utterances' prosodic pattern, such as phrase‐final lengthening or the post‐accentual pitch fall. Thus, although SRS in its present implementation allows only one level of explicit user‐defined synthesis unit, it is relatively easy to set up implicit units of the larger sizes needed to write straightforward prosody rules.

ISSN:0001-4966    

DOI:10.1121/1.2020478

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

The study population consisted of 196 male hourly workers from a noise exposed (>88 dBA) and 169 from a less noise exposed plant. Participants were 40–63 years of age and had at least 10 years of exposure. Clinical exams consisted of height, weight, pulse, blood pressure, audiometric testing, and occupational history. Body mass index, alcohol intake, and family history of hypertension were comparable for the two groups. There was a significant difference in the proportion of men with severe noise induced hearing loss (SNIHL) (>65 dB loss at 3, 4, and 6 kHz) between the two plants, as well as an increase in the number with hearing impairment. Other definitions of noise induced loss were explored and yielded similar results. A two‐way analysis of variance was conducted with mean systolic and diastolic blood pressure as the outcome variable with age as a covariate. The main effects of plant and SNIHL were found to be significant atp<0.05 for diastolic blood pressure only. There was a greater proportion of hypertensives in the 56 + age group with severe noise loss in both plants (p<0.003).

ISSN:0001-4966    

DOI:10.1121/1.2020521

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Measurements of sound exposure (n= 151) were recorded in children aged 6 to 18 years with Metrosonics dB 301 Metrologgers. For each child, a log equivalent sound level (Leq) and corresponding sound source were recorded for 480 separate 3‐min intervals during a 24‐h period. Data for each individual were summarized into 20 activity (sound source) categories, and anLeq(8) andLeq(t) computed for each, wheretis the total time spent engaged in a specific activity. Analysis of variance reveals highly significant differences inLeqs among activities, and Duncan's multiple range test suggests four groupings. Lawnmowers/combustion engines, live music, school bus, and school assembly/recess are major sound sources for children; each sound source has anLeq(t)>80 dB in boys and girls and average exposure duration of 0.5 to 2.1 h per day for those exposed. There is a significant sex difference in total sound exposure;Leq(24) = 77.8 ± 6.1 and 75.2 ± 5.3 in boys and girls, respectively. Boys appear to place themselves in a noisier environment than girls, since girls have a lower meanLeqthan boys for virtually every activity. [Work supported by EPA and USAF.]

ISSN:0001-4966    

DOI:10.1121/1.2020566

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Diffraction tomography is basically the inversion of an inhomogeneous Helmholtz equation, that is, the “reconstruction” of the inhomogeneity from observed field data. The underlying Helmholtz equation is an approximation (Born or Rytov's} to a general wave equation which describes sound propagation in viscoelastic media. The rather complex relationship of the inhomogeneity to the viscoelastic parameters of the object of interest is briefly described together with the nature of the approximation errors for Born and Rytov. The basic principles of data acquisition and image reconstruction as they apply to diffraction tomography are discussed for two cases of object insonification: plane wave and fan beam. Finally we examine the relative merits of frequency and spatial domain reconstructions with respect to computational efficiency and accuracy of interpolation. Several simulation and experimental examples are presented to show the effectiveness of this approach in practice. [Work supported by NSF Grant ECS‐7926008.]

ISSN:0001-4966    

DOI:10.1121/1.2020626

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

A technique for generating a target image utilizing acoustic transient response signature data is explained and demonstrated for elastic shells in water. The technique combines features of physical optics inverse diffraction and feature‐space target identification approaches. Complex harmonic backscattering spectrum in the low resonance range is used as input data for this approach. A periodic ramp in response waveform synthesized from these data is shown to be correlated to the cross‐sectional area versus distance along the line‐of‐sight, or profile function, of the targets measured. Visual images simulating an isometric view of the target are constructed.

ISSN:0001-4966    

DOI:10.1121/1.2020681

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

We summarize the status of the scattering of scalar waves from random surfaces for both coherent and incoherent applications. The usual surface descriptor is via a Gaussian probability distribution in height and, for homogeneous statistics, a correlation function (or its Fourier transform, the surface spectral function). For isotropic surfaces, this leads to a parametric surface description in terms of two independent dimensionless length scales involving wavelength, surface rms height, and correlation distance. For coherent scattering, Kirchoff and perturbation methods are valid for only small roughness. Integral equation methods (Dyson equation} extend the range of validity to larger roughness but further extensions face computability problems. Applications include long range propagation in waveguides with rough walls. Incoherent scattering is described using a Bethe‐Salpeter formalism which requires extensive approximations to be tractable. Some comparison with experiment will be given as well as a brief discussion of recent developments.

ISSN:0001-4966    

DOI:10.1121/1.2020230

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP