摘要:

Five monaural chinchillas were exposed to a repetitive, reverberant, impulse noise for ten days. The impulse‐noise source was a mechanized hammer hitting a steel plate at a rate of 1/s. The average, peak over pressure within the holding cage was 113 dB SPL. Auditory thresholds were determined before and after exposure at 0.5, 1, 1.4, 2, 2.8, 4, 8, and 16 kHz utilizing shock‐avoidance conditioning. During exposure, thresholds were monitored on a daily basis at 0.5 and 8 kHz. Within one hour from the start of the exposure, threshold shift at 8 kHz had reached an asymptotic level, while threshold shift at 0.5 kHz leveled off after 24 h of exposure. Asymptotic threshold shift (ATS) levels for both frequencies varied between 30 and 50 dB across animals. Median threshold shift for both frequencies recovered to within 10 dB of normal after 40 days of recovery. Maximum permanent threshold shift (PTS) was at 2 and 2.8 kHz with median PTS of 17 and 13 dB, respectively. After final thresholds were obtained (50–70 days), the cochleas were examined histologically using the surface preparation technique. A comparison is made between impulse‐noise‐induced ATS and ATS produced by continuous‐noise sources.

ISSN:0001-4966    

DOI:10.1121/1.381767

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Residue pitch was examined by means of adaptation. The monaural perceptibility of a residue pitch was measured before and after exposure to ipsilateral or contralateral adapatation stimuli of variable spectral composition. Several aspects of adaptation were investigated: pitch channel specificity, number of stimulus components necessary to adapt a residue channel, importance of temporal and spectral factors for adaptation, and the relation between pure‐tone and residue pitch. It was found that there are residue‐pitch channels specifically sensitive to the spectral region and ear of presentation of the stimulus. At least two harmonics were necessary to adapt a residue channel, and pitch channels were found to be insensitive to temporal factors. Residue and pure‐tone pitch seemed to be extracted by different mechanisms, haveing independent channels. The data presented augment the understanding of ptich perception and suggest refinements for pitch‐perception models.

ISSN:0001-4966    

DOI:10.1121/1.381768

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The simultaneous, ipsilateral masking of a sinusoid of frequencyfs(600–860 Hz), located near the common cutoff frequencyfc(750 Hz) of a low‐pass and high‐pass noise was examined as a function of the level of each of the bands. The pressure spectrum level of the high‐frequency bandLhranged from 5–50 dBre20 μPa in 15‐dB steps and the level of the low‐frequency bandL1was from 0–24 dB down from each of these levels. The computer‐synthesized noise provided a spectral step function transition atfc. The data generated by each of the three listeners in the 4IFC adaptive task was virtually identical. Whenfs≫fcmasking was determined simply byLh, and whenfs≪fcmasking was generally equal to but sometimes greater than that attributable solely toL1. Whenfs?fc, masking was intermediate relative to the asymptotic values just mentioned. The data are consistent with a conceptual auditory filter which has a Gaussian shape, an equivalent rectangular width of 110 Hz (for the limited frequency range considered), and a center frequency which is shifted away from the high‐band noise relative tofs. These characteristics are not dependent onLhalthough the asymmetry of filter positioning is weakly related toL1−Lh. The data are also consistent with a model which postulates that masking is a function of the simple sum of the masker power derived from the low‐band, high‐band, and internal noise appearing at the filter output.

ISSN:0001-4966    

DOI:10.1121/1.381769

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

In an attempt to clearly differentiate perceptual effects that are attributable to ’’auditory’’ and ’’phonetic’’ levels of processing in speech perception we have undertaken a series of experiments with animal listeners. Four chinchillas (Chinchillalaniger) were trained to respond differently to the ’’endpoints’’ of a synthetic alveolar speech continuum (0 ms VOT and +80 ms VOT) and were then tested in a generalization paradigm with the VOT stimuli between these endpoints. The resulting identification functions were nearly identical to those obtained with adult English‐speaking listeners. To test the generality of this agreement, the animals were then tested with synthetic stimuli that had labial and velar places of articulation. As a whole, the functions produced by the two species were very similar; the same relative locations of the phonetic boundaries, with lowest VOT boundaries for labial stimuli and highest for velar stimuli, were obtained for each animal and human subject. No significant differences between species on the absolute values of the phonetic boundaries were obtained, but chinchillas produced identification functions that were slightly, but significantly, less steep. These results are discussed with regard to theories of speech perception, the evolution of a speech‐sound repertoire, and current interpretations of the human infant’s perceptual proclivities with regard to speech‐sound perception.

ISSN:0001-4966    

DOI:10.1121/1.381770

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A method for reducing the characteristic buzz of LPC synthetic speech is presented. The method consists of the use of a nonimpulse source for exciting the LPC synthesizer during voiced sounds. One novel feature is that the temporal parameters of the source are kept in fixed proportion to the pitch period. An extensive perceptual experiment has shown that the resulting quality of the synthesis is significantly preferred over the quality of the standard LPC synthesis.

ISSN:0001-4966    

DOI:10.1121/1.381771

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

In order to investigate the nature of some processes in speech acquisition, synthetic speechlike stimuli were played to groups of English and French children between two and fourteen years of age. The acoustic parameters varied were voice onset time and first‐formant transition. Three stages were observed in the development of children’s labeling behavior. These were called scattered labeling, progressive labeling, and categorical labeling, respectively. Individual response patterns were examined. The first stage (scattered labeling) includes mostly children of two to three years of age for the English and up to about four for the French. Children label most confidently those stimuli closest in physical terms to those of their natural speech environment. All stimuli with intermediate VOT values are labeled quasirandomly. Progressive labeling behavior is found mostly amongst children aged three and four for the English, up to about seven for the French. Children’s response curves go progressively—almost linearly—from one type of label (voiced) to the other (voiceless): response follows stimulus continuum. Categorical labeling becomes the dominant pattern only at the age of five to six for the English, one or two years later for the French. This development was found to be highly significant (psmaller than 0.003 for both English and French, using Kendall’s tau measure of correlation). English children learn to make use of theF1 transition feature around five years, whereas French children never use it as a voicing cue. French children will have fewer features than English children at their disposal: This may account for the later age at which French children, as a group, reach the various labeling behavior stages, and for labeling curves being less sharply categorical for French than for English children. These findings indicate that categorical labeling for speech sounds is not innate but learned through a relatively slow process which is to a certain extent language specific. The implications of the results are discussed in the light of previous work in the field.

ISSN:0001-4966    

DOI:10.1121/1.381772

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Subjects tapped the beat (i.e., meter) of a polyrhythm in which one tone occurred three times per pattern repitition while the second tone occurred four times per pattern repitition. At one presentation rate, the polyrhythm underwent a figure‐ground reversal —the beat shifted from one tone to the other. Rhythmic organization is thus a function of the absolute tempo.

ISSN:0001-4966    

DOI:10.1121/1.381773

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A compilation, from the original papers, is presented of the data on the acoustic properties (i.e., velocity and attenuation) of mammalian tissues in the megahertz range of frequencies used in medical ultrasonics. The actual values reported have been quoted to present a clear picture of the current state of knowledge in order to enable it to be assessed and to enable future workers to compare their own results directly. In the 20 years since the last such compilation, the progress in estimating the relative contributions of the animal species, the condition of the tissue, the temperature and frequency at which measurements were made, and the method of measurement to the observed variation has been small. It is hoped that this compilation together with its summarizing tables will both be of practical use to the worker in the field and also encourage the establishment of a stronger body of fundamental information for the application of ultrasonics in biology and medicine.

ISSN:0001-4966    

DOI:10.1121/1.381774

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

We describe an efficient method for simulating the distributed response of complex asymmetrically branching networks which satisfy requirements of network self‐consistency. Individual tree links may be dispersive and lossy. As a case in point we simulate the response of the human lung, and characterize the variations in pressure with frequency, path, and position. The effects of tree asymmetry are found to be significant above 100 Hz in the air‐filled lung.

ISSN:0001-4966    

DOI:10.1121/1.381775

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The qualitative modal structure of lung response is investigated. Asymmetry of the branching airway network of the lung leads to clumping of system eigenvalues into distinct and well‐separated clusters at low frequency. The breadth of the eigenvalue clusters increases with the degree of asymmetry and frequency. At high frequency the breadth of the clusters exceeds the cluster spacing so that distinct eigenvalue clusters are no longer observed. Symmetric airway networks lead to degenerate mode clusters with large eigenvalue redundancy. The average density of eigenvalues of the undamped system is estimated to be higher than 0.5 per Hz. All modes appear to be in modal overlap.

ISSN:0001-4966    

DOI:10.1121/1.381776

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP