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Listeners' abilities to discriminate the order of two tones, of frequency 500 Hz and 500 Hz + delta f, separated by less than 5 ms, were measured in terms of threshold durations (T) for the tones. The experiment was repeated for values of delta f between 5 and 160 Hz. The relation of the duration threshold to delta f was well-described by the reciprocity equation, delta fT = K, for K = 0.16. This reciprocity corresponds to a constant overlap of the main lobes of the power spectra for the tones of about 70%-80%. Addition of a trailing context tone severely degraded the ability to discriminate temporal order, increasing the value of the reciprocity constant to approximately K = 1.8. The primary effect of the context tones was to increase the duration required for accurate discrimination, rather than to impair actual frequency resolution. Implications of these results for speech perception are discussed.

This study compared the reliability of a recently developed high-frequency audiometer (HFA) [Stevens et al., J. Acoust. Soc. Am. 81, 470-484 (1987)] with a less complicated system that uses supraaural earphones (Koss system). The new approach permits calibration on an individual basis, making it possible to express thresholds at high frequencies in dB SPL. Data obtained from 50 normal-hearing subjects, ranging in age from 10-60 years, were used to evaluate the effects on reliability of threshold variance, earpiece/earphone fitting variance, and the variance associated with the HFA calibration process. Without earpiece/earphone replacement, the reliability of thresholds for the two systems is similar. With replacement, the HFA showed poorer reliability than the Koss system above 11 kHz, largely due to errors in estimating the calibration function. HFA reliability is greater for subjects with valid calibration functions over the entire frequency range. When average correction factors are applied to the Koss data in an effort to convert threshold estimates to dB SPL, individual transfer functions are not represented accurately. Thus the benefit of being able to express thresholds at high frequencies in dB SPL must be weighed against the additional source of variability introduced by the HFA calibration process.

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.

Factors which determine the discriminability of tonal sequences, or patterns, were investigated in five experiments. The patterns were generally sequences of ten 40‐msec tonal components, which ranged in frequency from 256 to 900 Hz, or from 500 to 1500 Hz, in equi‐log intervals. Highly trained (15 to 60 h of training prior to collecting experimental data) listeners’ abilities to detect changes in the frequency of single tonal components in these patterns were measured using a same–different psychophysical method. The just‐detectable values of Δf (d′=1.0) were only slightly larger than for single 40‐msec tones presented in isolation for tonal components at the end of the temporal sequences (a ’’recency’’ effect). Performance was systematically worse for earlier components, the just‐detectable Δf increasing by four to five times from the end of the pattern to the beginning (no ’’primacy’’ effect). The ’’recency’’ effect was interpreted as a matter of later arriving components interfering with frequency res...

The onset of a noise (0.9‐2.1 kHz, 55 dB SPL) preceded that of a buzz (100 Hz, 0.5‐3.0 kHz, 70 dB SPL, 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 two responses of their choice such as “short noise” and “long noise” or “no noise” and “noise.” The results are highly similar to those reported for the phoneme boundary between voiced and voiceless synthetic plosive consonants. Discrimination was optimal across a 16‐msec noise‐lead time boundary and labeling shifted abruptly at the same noise‐lead time. The results can probably be accounted for in terms of judgment of temporal order or the difference limen for duration of the leading part (noise‐alone) of the stimulus.

A battery of eight auditory discrimination tests was designed to measure the primary dimension along which simple and complex sounds can be discriminated. Six of the tests, selected on the basis of data collected in an earlier 22‐subtest version of the battery [D. M. Johnson, J. K. Jensen, and C. S. Watson, J. Acoust. Soc. Am. Suppl. 1 67, S52 (1980)], use tonal stimuli: tests of frequency, intensity, and duration discrimination, using single tones, and tests of rhythm, temporal order, and tonal‐pattern discrimination using multitone sequences. Two additional tests employ speech sounds: a syllable order discrimination test and a modification of one portion‐ of a nonsense syllable identification test [J. R. Dubno and H. Levitt, J. Acoust. Soc. Am. 69, 249–261 (1981)]. The tape‐recorded tests were designed to be administered to groups of listeners in a free field, moderately low‐reverberation environment. with responses recorded on printed forms. Seventy‐two modified 2AFC trials, distributed among eight sti...

A form of “informational masking” is observed when listeners attempt to detect single target components of word‐length tonal patterns [J. Acoust. Soc. Am. Suppl. 1 64, S39 (1978)]. These masking‐like effects, sometimes as large as 50–60 dB, occur under conditions of high stimulus uncertainty, when contextual patterns and the temporal and spectral positions of target tones are varied from trial‐to‐trial, but are absent under conditions of minimal psychophysical uncertainty. Stimulus determinants of informational masking were investigated in three experiments, by (a) varying the duration of the contextual patterns from 0 to 400 ms, (b) varying the duration of the target tones from 20 to 160 ms, and (c) varying the spectral range for the contextual tones from 1 to 2700 Hz. Individual differences in asymptotic detection thresholds, and in training times required to approach those thresholds, are unusually large in these tasks. However, the data are generally characterized by the following rules. Informational masking approaches asymptotic levels for context durations in excess of 160 ms. Little or no masking occurs for target tones longer than 60–80 ms. Similar average amounts of masking were observed for each of the spectral ranges of the context tones. [Work supported by NIH.]

In a recent paper we described the decay of auditory memory for patterns consisting of ten 40‐msec tones played in sequence. On each trial, one of 50 permutations of a ten‐tone catalog was played, and then it was repeated either with or without a frequency increment (Δf) added to one of the ten tonal components. The interval between the two patterns was varied from 0.5 to 32 sec. The frequency increments became only slightly less detectible as the interstimulus interval was lengthened (just‐detectible values of Δf increased by about 1/3). In a new experiment, the same highly trained listeners were able to make almost as precise discriminations without a standard present on each trial. When the patterns consisted of ten‐tone sequences drawn from a 1000‐tone catalog the listeners could no longer perform at better‐than‐chance levels in the remembered‐standard conditions. The results begin to establish the limits of listeners' ability to learn the parameters of a catalog from which acoustic stimuli are sampled. [Supported by Grant No. NS03856, National Institute of Neurological Diseases and Stroke, Department of Health, Education and Welfare.]

Performance on several three‐alternative, temporal forced‐choice discrimination tasks (3AFC) was found to vary significantly over the three possible temporal positions of the signal on each trial. First observed in a ten‐tone pattern discrimination task, this temporal‐interval effect was also found to occur in a battery of 22 detecton and discrimination tests, designed for the study of individual differences in auditory capabilities by Johnson, Jensen and Watson [J. Acoust. Soc. Am. 67, S58 (1980)]. Interval‐specific indices of d′ and β were derived by decomposition of the 3 × 3 stimulus‐by‐response matrices for each task into 2 × 2 matrices. These measures suggest that the temporal‐interval effect is typically the result of a combination of decreased sensitivity in the early intervals and relaxed‐decision criteria for the later ones. Listeners with overall high levels of auditory resolving power in the individual‐differences test battery show the least temporal‐interval effect in 3AFC tasks. This last result suggests a dependence of both overall discrimination performance and the temporal‐interval effects on the relative efficiency of short‐term auditory memory. [Work supported by NIH.]

In two recent experiments we described the discriminability of acoustic patterns consisting of ten 40‐msec tonal components played in sequence, as measured with a same‐different psychophysical method. Listeners can readily discriminate two such patterns when the only difference is in the frequency of one of the ten tonal components, although values of the just‐detectible Δf increase by as much as an order of magnitude for early components as compared to later ones and for lower as compared to higher frequency components. In a new procedure listeners attempted to match the patterns by controlling the frequency of a single tonal component. They were able to routinely adjust that frequency within ± 10 Hz of its value in a standard pattern (which was presented in alternating sequence with the pattern in which they controlled the frequency of one component), although ± 60‐ to 100‐Hz values of Δf had been required for the same patterns to be discriminated in the same‐different procedure. Possible interpretations of this result are that the adjustment procedure enables extremely precise focusing of auditory attention, and that the site of intrapattern interference is more centrally located than previously suspected. [Supported by Grant No. 03856, National Institute of Neurological Diseases and Stroke, Department of Health, Education and Welfare.]

Auditory patterns, each composed of a sequence of 10 tones 40‐msec long with frequencies between 250 and 900 Hz, were played in pairs. The patterns within each pair were either the same or differed by a Δf added to one of the 10 tonal components. Just detectable values of this Δf are quite small when the same patterns are used on every trial and when listeners know which tonal component may be changed [Watson and Wroton, J. Acoust. Soc. Amer. 51, 113(A) (1972)]. Presenting a new pattern on each trial was found to make the task significantly more difficult; however, the increase in difficulty was uniform whether one, two, four, or eight tonal components comprised the catalog from which the one to be varied was selected. Decay of the “auditory image,” studied by varying the interval between standard and comparison patterns, was found to proceed at a rate similar to that for single tones.