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PubMed2002

A psychophysical theory of intensity proportions, joint presentations, and matches.

Empirically testable assumptions relate 3 psychophysical primitives: presentations of pairs of physical intensities (e.g., pure tones of the same frequency and phase to the 2 ears or 2 successive tones to both ears); a respondent's ordering of such signal pairs by perceived intensity (e.g., loudness); and judgments about 2 pairs of stimuli being related as some proportion (numerical factor, as in magnitude production). Explicit behavioral assumptions lead to 2 families of psychophysical functions, one corresponding to unbiased joint presentations and the other to biased ones. Under an invariance assumption, the psychophysical functions in the unbiased case are approximate power functions, and those in the biased case are exact power functions. A number of testable predictions are made. The mathematics involved draws from publications in utility theory and mathematics but with a reinterpretation of the primitives.

Humans↗
PubMed2004

Sequence effects in the categorization of tones varying in frequency.

In contrast to exemplar and decision-bound categorization models, the memory and contrast models described here do not assume that long-term representations of stimulus magnitudes are available. Instead, stimuli are assumed to be categorized using only their differences from a few recent stimuli. To test this alternative, the authors examined sequential effects in a binary categorization of 10 tones varying in frequency. Stimuli up to 2 trials back in the sequence had a significant effect on the response to the current stimulus. The effects of previous stimuli interacted with one another. A memory and contrast model, according to which only ordinal information about the differences between the current stimulus and recent preceding stimuli is used, best accounted for these data.

Humans↗
PubMed1989

Discriminability, loudness, and masking in the rat (Rattus norvegicus): a confirmation and extension.

In Experiment 1, rats discriminated between two sound pressure levels (SPL) of a pure tone: standard (STD) SPLs of 84 and 74 dB and comparison (CO) SPLs 4, 14, and 24 dB below STD were tested in quiet and 60 dB noise at 4 and 12.5 kHz (24 conditions). The decibel difference between STD and CO accounted for only 43.52% of the variance in the signal detection measure of sensitivity, d', across conditions, whereas the loudness difference (LD = STD0.35 - CO0.35) accounted for 89.82% of the variance in d'. These results confirm and extend previous observations that: (a) equal decibel differences are not equally discriminable; (b) loudness for the rat increases as a power function of SPL with an exponent of 0.35: and (c) masked loudness is a linear function of loudness in quiet. In Experiment 2, the assumptions of normal distribution and equal variance implicit in the use of the d' measure were examined. Receiver operating characteristic curves that were well approximated by straight lines of unit slope in normal-normal coordinates were obtained and thereby validated the use of d' in Experiment 1.

Animals↗
PubMed1992

Loudness bisection and masking in the rat (Rattus norvegicus).

The bisection method of animal psychophysical scaling was examined as a measurement procedure. The critical assumptions of bisection scaling, as described by Pfanzagl (1968), were tested to determine if a valid equal-interval scale could be derived. A valid scale was derived in which loudness for the rat (Rattus norvegicus; n = 13) was a power function of sound pressure for 4-kHz tones. Masking noise reduced the discriminability of tonal stimuli but did not affect the bisection point. This result is consistent with an interval scale representation of loudness and demonstrates scale meaningfulness. Loudness bisection data that have been reported in the literature for 3 species (humans, rats, and pigeons) are in substantial agreement with our results.

Animals↗
PubMed1997

Free-field binaural unmasking in budgerigars (Melopsittacus undulatus).

The detection of signals in noise is important for understanding both the mechanisms of hearing and how the auditory system functions under more natural conditions. In humans, the auditory system gains some improvement if the signal and noise are separated in space (binaural masking release). Birds with small heads are at a disadvantage in separating noise and signal sources relative to large mammals, because interaural time differences are much smaller. Two binaural phenomena in budgerigars related to the detection of tones in noise were examined. Budgerigars show 8 dB of free-field binaural masking release when signal and noise are presented to their right side and correlated noise is presented to their left side. Budgerigars also show a spatial masking release of 9 dB when a signal and noise are separated in azimuth by 90 degrees. These results are similar to those found in humans and other mammals with much larger heads.

Animals↗
PubMed1995

Lateralization of high frequency sounds as a function of interaural amplitude disparity.

Twenty-five subjects made graphic ratings of the perceived lateral position within the head of sounds presented through headphones. The stimuli were high frequency, pure tones and amplitude modulated sounds. For the amplitude modulated sounds, a 200 HZ modulation frequency was combined with carrier frequencies of 2200 HZ, 3200 HZ, 4200 HZ, and 5200 HZ, which were also the pure tone frequencies. Interaural level differences in the signals ranged from zero to 12 dB. The rate of lateralization was defined as the slope of the linear trend relating laterality ratings to interaural level differences. The rate of lateralization was found to be a decreasing function of frequency. The laterality ratings of amplitude modulated signals were nearly identical to those for pure tones. This result suggests that, for high frequency signals, conflicting temporal information that a source is centered is suppressed in favor of information from level differences that the source is off-center.

Adult↗
PubMed1980

Loudness scaling in rats and chinchillas.

Chinchillas and rats were trained on operant discriminations in which the discriminative stimuli were two different sound pressure levels of a 4-kHz tone. Two or more of these two-intensity discriminations were used at each of three levels of discriminability: high, medium, and low. For any given level, each of the stimulus pairs used differed in decibel separation but were similar in loudness-unit differences calculated from a power function. Different groups of animals trained on stimuli separated by equal numbers of loudness units produced equivalent performances at each of the three levels of discriminability. It is concluded that loudness growth for both of these species, as for man, is well described by a power function (Stevens' law). For the chinchilla the exponent is .25, and for the rat it is .35.

Animals↗
PubMed1980

Auditory intensity discrimination in blackbirds and pigeons.

Redwing blackbirds, brown-headed cowbirds, and pigeons were trained with operant conditioning techniques to respond to small increases in the intensity of pulsed tone trains at three frequencies: .5, 1.0, and 2.0 kHz. All three species produced similar intensity difference limens (DLs) at the frequencies tested. Intensity DLs decreased as sensation level (intensity level above absolute threshold) increased at all three frequencies, with the slopes of these sensation level functions being greatest at 2.0 kHz . The median intensity DLs at 50 dB sensation level were 3.3, 2.7, and 2.9 dB at .5, 1.0, and 2.0 kHz, respectively, averaged over the three species. Some subjects were also required to detect decreases in intensity. They produced intensity DLs two to three times larger than the DLs obtained when these same subjects were required to detect increases in intensity. Avian intensity DLs generally appear to be 1-2 dB higher than the DLs of those mammals that have been tested (rat, cat, monkey, humans).

Animals↗
PubMed1981

Postnatal development of absolute auditory thresholds in kittens.

Postnatal development of absolute auditory thresholds in the kitten was behaviorally measured from birth up to 1 mo of age. Unconditioned reactions to pure tones were observed for kittens up to Day 12, and conditioned responses were used for animals from Day 10 onward. At 1 day after birth, the first noticeable responses were obtained in 4 of 11 kittens at frequencies of .5-2 kHZ. At 2 days of age, 12 of 16 kittens responded. Thresholds remained high (above 100 dB SPL) up to the sixth day, but the range of behaviorally effective frequencies extended from .2 to 6 kHZ. All conditioned response thresholds at Day 10 and most at Day 12 were significantly lower than those measured by unconditioned reactions. From 10 days onward, all threshold curves showed a characteristic sensitivity optimum at 4 kHZ. For frequencies below 1 kHZ, maximum sensitivity was reached at Day 15; for frequencies up to 20 kHZ, at Day 20; and for even higher frequencies, at Day 30. At 1 mo of age, the frequency range is adultlike. The present behavioral results on developing acoustic function in the kitten closely followed structural maturation of the acoustic pathway and demonstrated limitations of the ability for acoustical communication during the first week of life.

Aging↗
PubMed1993

Neonatal movement response decrement and recovery to sounds as a function of stimulus intensity.

Response decrement, novelty response, and dishabituation of body movements to repeated presentations of a white noise stimulus of 66, 76, and 86 dB were studied in 89, 2-3-day-olds in the first epoch of active-quiet sleep following a feeding. Newborns receiving the 86 dB repeating stimulus had greater movement scores compared to those receiving the 76 dB intensity who, in turn, had greater movement scores than those receiving the 66 dB intensity. All groups demonstrated movement response decline following repeated stimulation and a novelty response was observed when either a 66 or 76 dB repeating stimulus was increased to 86 dB. A novelty response was not observed when intensity was decreased and dishabituation was not observed following a novelty response. For a white noise stimulus, these findings are more consistent with the selective adaptation than the habituation explanation of neonatal response decrement to repeated auditory stimulation.

Acoustic Stimulation↗
PubMed1990

Unmasking the magnitude estimation response.

The fuzzy judgement model of Ward (1979) predicts an inverse relation between the amount of stimulus information available to subjects and the magnitude of sequential dependencies on previous stimuli and responses in psychophysical scaling tasks. Ward confirmed this prediction for magnitude estimations of interdot distance for previous responses but not for previous stimuli, although the inverse relation has been repeatedly reported for both the previous stimuli and responses in absolute identification (e.g., Mori, 1989). This paper further explores this seemingly puzzling contradiction. A magnitude estimation of loudness experiment was conducted in which the amount of stimulus information available to subjects was manipulated by a modified version of informational masking (Watson, 1987). An absolute-identification-with-feedback experiment was also conducted to check the effectiveness of the informational masking in reducing the amount of stimulus information. The results of the magnitude estimation experiment show a striking similarity with those of Ward and generalize the failure of sequential dependencies on previous stimuli to vary inversely with stimulus information. An additional assumption that judgement strategies are altered under low-information conditions is necessary to explain this result.

Feedback↗
PubMed2001

Loudness constancy with varying sound source distance.

At a listener's ears, sound source power and sound source distance are confounded in measures of acoustic intensity, a physical property long thought to be the primary determinate of loudness. Although the relationship between sound source loudness and power is well known when source distance is fixed, relatively little is known about source loudness under conditions of varying distance. Here we show a robust loudness constancy, similar in many ways to visual size constancy, that results under distance-varying conditions that produce inaccurate estimates of source distance. Our results suggest that the auditory system does not require accurate distance estimates to judge source loudness, even when distance is variable. We offer an alternative explanation of loudness constancy based solely on a reverberant sound energy cue.

Acoustic Stimulation↗
PubMed2000

Properties of sound.

Basic concepts about sound exposure are reviewed without extensive reliance on the technical details of physical acoustics or psychoacoustics. The frequencies and intensities of sounds that might be encountered in a hospital nursery are described. Examples of the nonlinear properties of sound levels are provided. The complexities of adding and subtracting decibels are discussed. Some important noise standards are reviewed, along with an explanation of why some sounds might be more annoying than others. A companion article in this issue gives practical information on how to make sound-level measurements.

Acoustics↗
PubMed2004

Most comfortable and uncomfortable loudness levels: six decades of research.

This article critically reviews the influence of such factors as psychophysical testing method, stimulus type, and instructional set on most comfortable loudness (MCL) and uncomfortable loudness (UCL) levels. Generally, research indicates that test methods and instructions strongly affect both MCL and UCL while stimulus conditions affect them less substantially. Overall, the data suggest lower reliability for MCL than for UCL and lower reliability for pure-tone MCLs than for speech MCLs. Lower MCLs are typically obtained when measured by an ascending approach, in contrast to a descending approach. Results suggest that audiological efforts should be directed toward the development of a standardized test procedure that yields adequately reliable and valid MCLs and UCLs for routine clinical use.

Audiometry, Pure-Tone↗
PubMed2004

Effects of test order on most comfortable and uncomfortable loudness levels for speech.

This study examined test-order effects on most comfortable loudness (MCL) and uncomfortable loudness (UCL) levels for spondaic words in 2 groups of 30 normal hearing listeners each. For Group 1, MCL was measured first, followed by UCL. For Group 2, UCL was measured first, and then MCL. A retest was conducted for both groups. Results showed that MCL was significantly elevated for Group 2, but not for Group 1. There was no effect on UCL for either group. In a follow-up experiment, the magnitude of the test-order effect on MCL increased significantly when MCL measurements followed UCL measurements closely in time. These results argue for management of the ordering and temporal spacing of MCL and UCL testing in clinical loudness measurements.

Adolescent↗
PubMed2001

Speech motor stability in IPD: effects of rate and loudness manipulations.

Increasing phonatory effort, an integral component of the Lee Silverman Voice Treatment, LSVT, has been identified as an effective management strategy for adults with hypokinetic dysarthria associated with Parkinsonism. The present study compares the effects of increased loudness on lower lip movements to those of changes in speaking rate, another approach to the treatment of hypokinetic dysarthria. Movements of the lower lip/jaw during speech were recorded from 8 adults with IPD, 8 healthy aged adults, and 8 young adults. The spatiotemporal index (STI), a measure of spatial and temporal variability, revealed that for all speaker groups slow rate was associated with the most variability. Compared to the other conditions, STI values from the loud condition were closest to those from habitual speech. Also, the normalized movement pattern for the loud condition resembled that of habitual speech. It is hypothesized that speaking loudly is associated with a spatial and temporal organization that closely resembles that used in habitual speech, which may contribute to the success of the LSVT.

Aged↗