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A procedure is described that allows groups of subjects to be tested using adaptive psychophysical procedures when equipment limitations or experimental design requires each member of the group to be presented with the same stimuli. Group-vote rules are used to classify the group response on any trial as correct or incorrect, and this classification is used as input to standard, single-subject, adaptive procedures. The relationship between the probability of a correct group response and the probability of a correct individual response is derived by assuming members of the group respond independently and have identical psychometric functions. This relationship is used to choose a group-vote rule and an adaptive procedure that leads to a probability of correct individual response at convergence that is close to that which is desired. The usefulness of this procedure is limited to experiments where individual subjects have similar psychometric functions. It has, however, been used extensively for small groups of subjects to collect simple auditory discrimination data. [ABSTRACT FROM AUTHOR]

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 stimulus values, are presented in each of the discrimination tests. Performance of groups of listeners given successive versions of the test battery show it to be a reliable screening instrument for the measurement of auditory discrimination abilities. [Work supported by NIH/NINCDS.] [ABSTRACT FROM AUTHOR]

Previous studies of resolution of the frequency, intensity, and duration of individual elements of word-length tonal sequences have shown major degrading effects of trial-to-trial stimulus uncertainty. The same degree of stimulus uncertainty was recently found to cause elevations of detection thresholds of 40-50 dB above the levels expected from temporal masking [Watson, Kelly, and Mellen, J. Acoust. Soc. Am. 66, S83 (1979)]. We referred to the effect of stimulus uncertainty on the threshold of individual elements of patterns as informational masking. In the current experiment, we investigated the relation between the amount of informational masking and frequency discrimination for the same target tones. Detection and discrimination trials were interleaved in an adaptive psycho-physical sequence to measure observers' detection thresholds and frequency difference limens for a 45-ms, 1688-Hz target tone, presented 90 ms after the onset of a 10-tone pattern. Context (non-target) tones varied between 25-45, 35-55, or 65-85 dB SPL in level, 300-3000 Hz in frequency, and 25-105 ms in duration. Target-tone levels on frequency discrimination trials were 35, 45, 55, or 75 dB. Informational masking was found to increase 10 dB for each 10-dB increase in context level, essentially as does energy masking, although the source of the two effects is clearly different. At all negative sensation levels, the threshold values of ΔF were those required to shift target-tone frequency beyond the limits of the pattern bandwidth. Frequency discrimination improved systematically as current 'effective' sensation level increased from 0.0 to 40-50 dB, yielding a range of just-detectable values of Δf from over 1000 to about 20 Hz. The relation between sensation level and frequency discrimination is thus quite similar for informational and energy masking. [Work supported by NIH.] [ABSTRACT FROM AUTHOR]

Observers were asked to discriminate the temporal order of two tones with frequencies 550 Hz and (550 + ΔF) Hz. The interval between the tones was 5 ms. Tones were of equal duration, were linearly gated with 2.5 ms rise/decay, and were presented at 75 dB SPL. The psychophysical method was a modified two-alternative-forced-choice procedure in which the stimulus sequence designated as the 'signal' was presented before each pair of observation intervals. Tone durations were varied according to a transformed-up-down adaptive rule (Levitt, 1971) which converged on the durations required for 71% correct responses. Testing was done primarily for frequency separations of ΔF = 5, 10, 20, 40, and 80 Hz. Results indicate that for the frequency separations used, observers require tone durations which result in a constant amount of spectral overlap. For example, frequency differences of 10 and 40 Hz result in tone durations of 20 and 8 ms, respectively, to maintain 71% correct responses. Introduction of 100-ms leading and trailing tones at the geometric mean of the target-tone frequencies yields marked increases in tone-duration thresholds, with the degrading effect of the trailer alone nearly as large as that of the leader and trailer combination. [Work supported by NIH.] [ABSTRACT FROM AUTHOR]

The discrimination of word-length tonal patterns has previously been shown to be strongly dependent on the level of stimulus uncertainty of the psychophysical procedure employed [Watson, Kelly, and Wroton, J. Acoust. Soc. Am. 60 (1976)]. An experiment was conducted to determine the range of stimulus uncertainty effects and the time course of discrimination training, under various levels of stimulus uncertainty. Listeners were taught to detect differences between tonal patterns using a three-alternative, forced-choice adaptive psychophysical procedure. The differences to be detected were increments in frequency, level, or duration of one of four target tones whose frequency, duration, intensity, and temporal position were constant in the standard patterns. Asymptotic discrimination performance for the 45-ms target tones presented in the context of a temporal sequence of ten tones with a total duration of 450-ms, ranged from mean threshold values of ΔI, ΔT, ΔF of 13 dB, 40 ms, and 1100 Hz, respectively, under the highest levels of stimulus uncertainty, to levels only slightly greater than those measured for the target tones in isolation. [Work supported by a Biomedical Research Development Grant from NIH.] [ABSTRACT FROM AUTHOR]

Extremely imprecise resolution of the components of word-length tonal sequences, under conditions of high stimulus uncertainty, has led us to reconsider an earlier conclusion about the effective level of the components of such patterns. Watson and Spiegel [J. Acoust. Soc. Am. 58, S84 (1975)] reported that temporal masking of individual components of the tonal patterns used in their experiments amounted to no more than 15-20 dB. The sensation levels of the 75 dB SPL components of their patterns were therefore estimated to be at least 40-50 dB, which provided no explanation for extremely poor temporal, spectral, and intensive resolution of those components. We now realize that an erroneous conclusion was made in that experiment, since resolution measured under high stimulus uncertainty was compared to detection thresholds measured in a minimal-uncertainty procedure. When component thresholds are measured under conditions of minimal, intermediate, and high stimulus uncertainty, the sensation levels of 75-dB SPL components range from 50 to -5 dB, values consistent with listener's resolution of the same components. [Work supported by a Biomedical Research Development Grant from NIH.] [ABSTRACT FROM AUTHOR]

We have recently reported that frequency resolution, under conditions of high stimulus uncertainty, is much more accurate for late high-frequency components than for early, low-frequency components of word-length tonal sequences [Watson, Wroton, Kelly, and Benbassat, J. Acoust. Soc. Am. 57, 1175-1185 (1975)]. We have now replicated these experiments for the case of temporal resolution. Listeners were tested with high, medium, and minimal stimulus uncertainty until they performed at asymptotic levels of temporal resolution, defined by just-detectable proportional increments (Δt/t) in the duration of single 40-msec components of 10-tone sequences. The duration of late, high-frequency components is also resolved more accurately than that of early, low-frequency elements, although the differences are considerably less than for frequency resolution. Asymptotic just-detectable values of Δt/t range from about 0.75 to 0.15, from high to minimal levels of stimulus uncertainty, suggestive of a shift from detecting increments in tonal sequence duration to detecting increments in the duration of single test components. [Supported by Grant [sharp/mesh/hash_synonym]NS-03856 from NINCDS.] [ABSTRACT FROM AUTHOR]

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.] [ABSTRACT FROM AUTHOR]

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.] [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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.

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.