James D. Miller

Speech perception by the chinchilla: Identification functions for synthetic VOT stimuli

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 (Chinchilla laniger) 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 differenc...

Discrimination and labeling of noise–buzz sequences with varying noise‐lead times: An example of categorical perception

The onset of a noise [0.9–2.1 kHz, 55 dB SPL (A weighted)] preceded that of a buzz [100 Hz, 0.5–3.0 kHz, 70 db SPL (A weighted), 500 msec] by −10 to +80 msec and both terminated simultaneously. Eight adults discriminated among noise‐lead times in an oddity task. In separate sessions, they labeled singly presented stimuli with either of the two responses: ’’no noise’’ or ’’noise.’’ The results are highly similar to those reported for the categorical perception of synthetic plosive consonants differing in voice‐onset time. On the average, discrimination was best across a noise‐lead‐time boundary of about 16 msec, where labeling also shifted abruptly. These results and those of categorical perception, generally, are interpreted in terms of Weber’s law as applied to a single component within a stimulus complex. It is concluded that categorical perception of sounds is not unique to speech and suggested that it may be a general property of sensory behavior.Subject Classification: [43]65.75; [43]70.30.

Effects of noise on people

An overview of the effects of noise on people as can be determined from the scientific literature is presented. Only audible noise is considered and no attempt is made to describe the extent of the noise problem in terms of the number of people affected or in terms of social and economic costs. Rather, emphasis is placed on describing and classifying the adverse effects and relating them in a general way to the intensive and temporal properties of audible noise. For simplicity, the intensive dimension of the noise is usually given as the A‐weighted sound level and detailed descriptions and evaluations of various acoustical measurements are for the most part avoided. The effects of noise are classified as auditory, general psychological, and sociological, or as general physiological. A summary is included.

Audibility curve of the chinchilla

The audibility curve of the chinchilla was measured by behavioral audiometry. The animals were trained to respond to tones by the method of instrumental avoidance conditioning. Threshold tests were conducted in a sound‐treated quiet room, with the loudspeaker located over the chinchillas head. Thirty‐six chinchillas were made monaural by surgical destruction of the left cochleas. Their auditory sensitivity was measured for tones spaced at equal logarithmic intervals over the range from 0.09 to 22.8 kHz. In addition, a few animals were tested at 32.0 kHz. For tones between 0.62 and 6.0 kHz, the chinchillas threshold is about 2.4 dB sound‐pressure level (SPL). For low frequencies, sensitivity declines about 5 dB/oct from 0.62 to 0.19 kHz, and about 17 dB/oct from 0.19 to 0.09 kHz. For high frequencies, sensitivity declines about 7 dB/oct from 6.0 to 16.0 kHz, and about 22 dB/oct from 16.0 to 22.8 kHz. Similar measurements were made for 10 binaural chinchillas. On the average, the binaural animals are 2.0–...

Hazardous Exposure to Intermittent and Steady‐State Noise

The following document was prepared by NAS‐NRC CHABA Working Group 46. This group was asked to specify damage‐risk criteria for exposure to sound. The paper contains graphs of maximum sound‐pressure levels and durations of exposures that the Working Group believes would be tolerable and examples of the use of these graphs in addition to background information and a discussion of the rationale, assumptions, limitations, and general problems pertinent to the development and application of a damage‐risk criterion and related exposure contours.

A frequency‐position map for the chinchilla cochlea

Frequencies of tones are mapped on to distances along the organ of Corti by associating behaviorally measured threshold shifts with regions of hair-cell loss. The central tendency found for 95 frequency-position matches by four observers on 21 ears is approximated by a straight-line, log-linear relation between frequency and position. Only a small portion of the considerable variation of individual matches around this function could be explained by length of the organ of Corti. Other unidentified factors appear to be responsible for most of these variations.

Discrimination of auditory target dimensions in the presence or absence of variation in a second dimension by infants

Discrimination of two acoustic dimensions of auditory stimuli, vowel identity and pitch contour, was tested with infants between the ages of 4 and 16 weeks using the high-amplitude sucking (HAS) technique. Discrimination of the vowel dimension and the pitch dimension was tested under two conditions: when a change in the target dimension occurred in theabsence of constant variation in a second dimension, and when a change in the target dimension occurred in thepresence of constant variation in a second dimension. In addition, discrimination was tested in a combined condition in which one level of the vowel dimension was always combined with one level of the pitch dimension and the stimulus change to be detected was a recombination of the levels of each dimension. Sucking-recovery scores demonstrated that infants always discriminated a change in the target dimension when it occurred without variation in the second dimension, regardless of the dimension that served as the target. However, while variation of the pitch dimension did not alter vowel discrimination, variation in the vowel dimension interfered with discrimination of the pitch dimension. Discrimination was also not evidenced in the combined condition. Analysis of the group time-to-habituation (TH) data revealed that significantly longer TH scores were correlated with a failure to demonstrate discrimination. The data are discussed in terms of the formation of auditory perceptual categories in early infancy as they relate to the acquisition of speech and language and, more generally, to developmental attention and memory for auditory stimuli.

Speech perception by the chinchilla: discrimination of sustained ‖a‖ and ‖i‖

Four chinchillas were trained to respond differently to sustained ‖a‖ and ‖i‖. The ensemble of vowels included two repetitions of each of the vowels by each of four talkers at each of three pitch levels for a total of 24 ‖a‖’s and 24 ‖i‖’s. The sound levels of the vowels were randomly changed from trial to trial over a 10‐dB range. The animals easily transferred the training to a new set of vowels produced by 24 new talkers. Subsequently, the animals similarly transferred to synthetic ‖a‖’s and ‖i‖’s. The only relevant difference between the synthetic vowels was their formant structure, while there were irrelevant differences in their pitch contours. We conclude that the chinchilla can abstract some essential difference(s) between sustained ‖a‖ and ‖i‖ and ignore irrelevant variations of sound level, pitch level, pitch contour, and voice quality. These results are discussed in terms of perceptual learning and auditory concept formation.Subject Classification: 70.30; 65.75; 80.50.

Auditory Sensitivity and Song Spectrum of the Common Canary (Serinus canarius)

The auditory sensitivity of one strain (Belgian Waterschlager) of common canary (Serinus canarius) was measured by behavioral audiometry. Four birds were trained by instrumental avoidance conditioning in a double‐grille cage, and their thresholds for pure tones (0.25–9.0 kHz) were measured. Auditory sensitivity is greatest between 2.0 and 4.0 kHz with a possible maximum at 2.8 kHz, declines about 15 dB/oct for frequencies below 2.0 kHz, declines about 25 dB between 4.0 and 8.0 kHz, and 13 dB between 8.0 and 9.0 kHz. The acoustic power in the songs and calls of the Belgian Waterschlager falls primarily in the range 1.8–4.5 kHz as do the critical frequencies of a substantial proportion of the neural units in the cochlear nucleus of the canary. Thus, the auditory sensitivity and the neural machinery of the peripheral auditory system appear to be matched to the long‐term‐average power spectrum of the songs. In addition, these facts are compared to those for other birds and mammals, and speculations as to some...

Temporary Changes of the Auditory System due to Exposure to Noise for One or Two Days

A subject was exposed on two occasions to an octave band of thermal noise centered at 500 Hz. The first noise exposure was for 48 h at 81.5 dB SPL. Five weeks later, the second was for 29.5 h at 92.5 dB SPL. Auditory function was evaluated by several types of measurements made prior to an exposure, during periods of quiet interspersed within an exposure, and at various times after an exposure. Temporary threshold shift (TTS) measured after 4 min of quiet (TTS4) increased for the first 8–12 h of exposure and then remained constant as the exposure was continued. At 750 Hz, the value of TTS4 at asymptote was 10.5 dB for the 81.5‐dB exposure, and 27.5 dB for the 92.5‐dB exposure. Recovery from TTS required 3–6 days. While TTS was present: (1) the time constant of temporal integration was reduced at 750 Hz; (2) there was delayed recruitment of loudness; (3) the amplitudes of the Bekesy tracings were reduced; (4) frequency discrimination was unaffected; and (5) threshold shifts measured by evoked‐response audio...