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Speech-elicited acoustic reflexes and three measures of subjective loudness perceptions were administered to 10 normal ears and to 20 ears with confirmed sensorineural hearing loss. Most notable was the comparison between loudness discomfort level and the acoustic reflex, revealing a limited relationship. The use of the acoustic reflex as a clinical predictor of loudness discomfort is questioned.
In binocular brightness perception a phenomenon called Fechner's paradox can be observed. This paradox implies non-monotonicities in the psychometric functions of binocular brightness. Lehky (1983) proposed a model that describes such non-monotonicities. He suggested that Fechner's paradox also exists in binaural loudness perception. However, until now no sufficient data have been collected to test this hypothesis. Therefore, an experiment was conducted in which 36 psychometric functions were obtained using binaural stimuli in the range of intensities in which Fechner's paradox supposedly occurs. As a result, no significant non-monotonicities were found. However, it is shown that jnds derived from the psychometric functions contradict predictions derived from the limited binaural additivity model of Gigerenzer and Strube (1983).
The effect of masking noise on the temporal summation of loudness is investigated here by performing loudness balances between a standard 500-msec tone burst (1000 Hz at either 20-, 50-, or 80-dB SPL) and either masked or unmasked comparison tone bursts (1000 Hz with durations between 10 and 640 msec). In all but two instances, the obtained functions relating SPL for equal loudness to stimulus duration could be plotted as two line segments that met to form a knee. The slopes of the line segments at durations less than the kneepoints are altered by the masking noise, becoming less steep with increased masking. The rate of the slope decrease is related to the standard sound pressure level (SPL) and is greatest using the 80-dB SPL standard and least with the 20-dB SPL standard. Temporal summation of loudness continues at durations above the kneepoints. However, the obtained slopes are less than those found below the knee, and are independent of the test conditions. The slope changes are found to be related to the noise producing a power transformation on the operating characteristics of the auditory system. These latter findings are discussed in relation to Zwislocki's quantitative theory of the temporal summation of loudness.
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To estimate the relationship between musical preference and perceived loudness, 25 subjects, musicians and nonmusicians, were asked to match the loudness of a neutral stimulus to a given musical selection. Ten different types of music were used; each was rated for likability by the subject. Over-all analysis of loudness ratings indicated that nonmusicians were more accurate in matching loudness of a neutral stimulus with the musical selections. This finding suggests differences in loudness perception between musicians and nonmusicians. Both groups were most accurate on the selection which could be inferred as most familiar.
In this paper, we describe an extension of our preliminary theory of intensity resolution [Durlach and Braida, J. Acoust. Soc. Am. 46, 372-383 (1969)] to include loudness comparisons among different types of stimuli. The extended theory relates mean loudness matches to discrimination and provides a framework for the interpretation of results on the intrasubject variability of loudness comparisons. The predicted relation between mean loudness matches and discrimination is essentially the same as that proposed by Riesz [J. Acoust. Soc. Am. 5, 211-216 (1933)]. With regard to the variability of loudness comparisons, the extended model is essentially the same as the preliminary model except that a new term is included in the trace-mode memory variance to account for the dissimilarity of the stimuli being compared. The model is compared to some published data on loudness matching and discrimination and to some new data of our own on the variability of loudness comparisons obtained in a two-interval, roving-level, loudness-discrimination experiment.
This article explored the slippery context effect: When Ss judge the loudness of tones that differ in sound frequency as well as intensity, stimulus context (relative intensity levels at the 2 frequencies) can strongly influence the levels that are judged equally loud. It is shown that the size of the slippery context effect depends on the frequency difference between the tones: Small frequency differences (less than a critical bandwidth) produced essentially no slippery effect; much larger differences produced substantial effects. These results are consistent with a model postulating the existence of a central attentional or preattentive "filter-like" process whose weighting coefficients represent the size of the absolute as opposed to the relative (contextual) component of loudness perception and judgment.
Although hearing aids have shown little outward change in the past decade, the development of new components has produced a steady reduction in size and improvement in performance. The near-perfect electret condenser microphone occupies a mere 50 cubic millimeters and its low vibrational sensitivity permits close packing of components without acoustic feedback problems. The integrated circuit packs a hundred components into each cubic millimeter and has allowed the miniaturization of complex aids while simultaneously boosting performance. Integrated circuits will permit future aids to compensate distorted loudness perception as a function of frequency, and extract speech signals buried in noise. These sophisticated, computerized, hearing aids will demand new evaluation and fitting methods and it is the methodology rather than the technology that will pace their development.
Three experiments were performed to examine the reverberation cue to egocentric auditory distance and to determine the extent to which such a cue could provide 'absolute', as contrasted with 'relative', information about distance. In experiment 1 independent groups of blindfolded observers (200 altogether) were presented with broadband noise from a speaker at one of five different distances (0.55 to 8 m) in a normal hard-walled room. Half of each group of observers were presented with the sound at 0 deg azimuth, followed (after a delay) by the identical sound at 90 deg azimuth. The order of presentation was reversed for the remaining observers. Perceived distance varied significantly as a function of the physical distance to the speaker, even for the first presentations. The change in the binaural information between the 0 deg and 90 deg presentations did not significantly modify the results. For both orientations, near distances were overestimated and far distances were underestimated. Experiment 2 and 3 were designed to evaluate how much prior auditory exposure to the laboratory environment was necessary. A 200 Hz square-wave signal was presented from one of three distances (1, 2, or 6 m) to observers who had either minimal room information or an exposure which included talking within the room. Perceived distance varied significantly with physical distance regardless to exposure condition.
A model of auditory object formation and an experimental evaluation of the model are described. Specifically, predictions for intensity discrimination and interaural time difference discrimination for the central component of a three-component harmonic complex are evaluated empirically. The onset time of the central, target component is varied relative to the onset times of the remaining, interferer components in order to vary the degree of fusion (versus perceptual segregation) of the target and the interferers. The model, which is based on the idea of attenuation of the components in the nonattended auditory image (in the case of segregated images), predicts lower sensitivity to information at the target component for the fused versus segregated target, and equal sensitivities for completely segregated targets and targets presented in isolation. Results are presented for four subjects with component frequencies of 400, 600, and 800 Hz and with onset time differences of 0 or 250 ms. The target duration was always 100 ms and offset times were the same for all components. The subjective results were as expected, with synchronous onsets yielding one sound object, and asynchrony of the central component yielding two sound objects. Also, the empirical results on interference in the synchronous case were in qualitative agreement with the above predictions. However, significantly more interference was found than was predicted for both synchronous and asynchronous conditions. In fact, the amount of interference found contradicts the simple attenuation model of object formation.
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Speakers change the level of their voice when they listen to noise or hear their own speech amplified: When noise level is increased the voice becomes louder, whilst the response to speech amplification is a reduction of voice level. The question posed here is whether, when the level of various sounds concurrent with vocalisation is raised, the direction of the vocal level response is like that to the speaker's speech or like that to noise. Voice level was measured in response to speech, white noise, delayed auditory feedback, frequency-shifted speech, and noise created by an "Edinburgh masker". Selection of these sounds was governed by the role they have played in the explanation and treatment of stuttering. Fluent speakers and stutterers increased voice level when played delayed auditory feedback, the Edinburgh masker, or white noise; they reduced the level slightly in the remaining conditions. These results are used to assess auditory feedback monitoring accounts of the speech behavior of fluent speakers and stutterers, and some implications for the treatment of stuttering are pointed out.
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Real-ear measurements of the aided Loudness Discomfort Level (LDL) were obtained from five hearing-impaired listeners who were fit with two Class A and two Class D linear hearing aids, each with a different saturation sound pressure level (HFA SSPL90). These measurements were obtained with 75 dB SPL continuous discourse to determine whether saturation-induced distortion contributes to the sensation of loudness. Real-ear coherence measurements made at LDL were used to determine the extent of saturation, and sound quality judgments were used to determine whether the distortion present at LDL affected sound quality. Results indicated that the SPL, coherence, and sound quality ratings obtained at LDL were all higher for Class D hearing aids with relatively high HFA SSPL90 than for Class A hearing aids with relatively low HFA SSPL90. Overall results were generally consistent with the hypothesis that distortion affects both sound quality and the perception of loudness.
Prepulse inhibition of the startle reflex has been used as an animal model for information processing deficits found in some types of schizophrenia. These deficits may be mediated by hypersensitive dopaminergic systems. In the present study, the effects of subchronic d-amphetamine administration [2 mg/kg intraperitoneally (IP)] on prepulse and gap inhibition of the startle reflex were compared to the effects of acute amphetamine and saline administration on startle inhibition. Results of three experiments are reported. The first two experiments were used to select prestimulus parameters sensitive to changes in stimulus intensity on the one hand, and prestimulus parameters sensitive to temporal aspects of stimulus processing on the other hand. Because schizophrenics have problems with the temporal sequencing of information, prestimulus inhibition of the startle reflex was expected to be more pronounced when prestimulus processing depended predominantly upon temporal factors. Results supported this hypothesis, although the effects of d-amphetamine were found at near detection threshold duration only. Subchronic amphetamine had no effect on the neuronal mechanisms underlying inhibition of the startle reflex by prestimuli. The results also suggested that a careful selection of duration and intensity of the prestimulus may increase the sensitivity of the prestimulus-startle paradigm for the effects of drugs, for example.
In a variant of duplex perception with speech, phoneme perception is maintained when distinguishing components are presented below intensities required for separate detection, forming the basis for the claim that a phonetic module takes precedence over nonspeech processing. This finding is replicated with music chords (C major and minor) created by mixing a piano fifth with a sinusoidal distinguishing tone (E or E flat). Individual threshold intensities for detecting E or E flat in the context of the fixed piano tones are established. Chord discrimination thresholds defined by distinguishing tone intensity were determined. Experiment 2 verified masked detection thresholds and subliminal chord identification for experienced musicians. Accurate chord perception was maintained at distinguishing tone intensities nearly 20 dB below the threshold for separate detection. Speech and music findings are argued to demonstrate general perceptual principles.
Two experiments are reported that examine the preferred increase in intensity for creating a percept of half auditory distance from a reference. The results of both experiments indicate that the use of an inverse square law (increments of 6 dB) is not the best signal-processing method for this purpose. The application of the results is potentially useful towards the software design of 3-D auditory display systems that manipulate the perceived distance of auditory inputs in relationships to actual distances of physical objects.
Unconscious or subliminal perception has historically been a thorny issue in psychology. It has been the subject of debate and experimentation since the turn of the century. While psychologists now agree that the phenomenon of visual subliminal stimulation is real, disagreement continues over the effects of such stimulation as well as to its existence in other sensory modalities, notably the auditory. The present paper provides an overview of unresolved issues in auditory subliminal stimulation which explains much of the difficulty that has been encountered in experimental work in this area. A context is proposed for considering the effects of auditory subliminal stimulation and an overview of current investigations in this field is provided.