A model of top-down gain control in the auditory system

To evaluate a model of top-down gain control in the auditory system, 6 participants were asked to identify 1-kHz pure tones differing only in intensity. There were three 20-session conditions: (1) four soft tones (25, 30, 35, and 40 dB SPL) in the set; (2) those four soft tones plus a 50-dB SPL tone; and (3) the four soft tones plus an 80-dB SPL tone. The results were well described by a top-down, nonlinear gain-control system in which the amplifier’s gain depended on the highest intensity in the stimulus set. Individual participants’ identification judgments were generally compatible with an equal-variance signal-detection model in which the mean locations of the distribution of effects along the decision axis were determined by the operation of this nonlinear amplification system.     

The additivity of loudness across critical bands: A conjoint measurement approach

Five subjects were required in each trial to compare directly two sounds and to indicate which sound was louder. Each of the 64 sounds employed consisted of a combination of one of eight intensity levels of a 2-kHz tone and one of eight intensities of a 5-kHz tone. If, as Fletcher and Munson (1933) argued, loudness is additive for tone combinations in which the frequencies are widely separated, then subjects’ judgments should reflect the summed loudnesses of the 2- and 5-kHz tones in a two-tone combination. Judgments of individual subjects were shown to satisfy the conditions for an additive structure, and individual loudness scales were constructed. These loudness scales varied from subject to subject. Since this paired comparison procedure minimized response biases, the results suggest substantial individual differences in the sensory representation of sound intensity. The relations among sensory scales derived from other structured sensory judgments, such as binaural loudness, are discussed.     

Induced loudness reduction as a function of frequency difference between test tone and inducer

When a high-intensity tone (inducer) is followed by a moderate-intensity tone (test tone), the loudness of the latter is reduced. This phenomenon, called induced loudness reduction (ILR), depends on the frequency separation of the two tones; as the difference in frequency increases, the amount of ILR decreases. However, the precise course of this decrease is not well known. This article presents two experiments that address this question. In the first experiment, the amount of loudness reduction produced by a 2.5-kHz 80-dB-SPL inducer was measured with the frequency of the test tone swept from 800 Hz to 6 kHz. In the second experiment, the amount of ILR was measured with the same inducer and with test tones set at 2, 2.5, 3, and 4 kHz. Both experiments show that some ILR occurs at frequency separations as wide as four critical bands.     

Effects of stimulus context on magnitude estimations and category ratings of perceived loudness--the spacing of intensity intervals

Effects of stimulus context on magnitude estimations and on category ratings were examined for a range of stimulus intensities of a 1-kHz tone. The stimuli were distributed in equal-interval steps of energy so they formed a perceptual cluster of high-intensity tones with a perceptual outlier at the lowest intensity. According to the Invariance Principle, the shape of the response function should not be affected by the distribution of stimulus intensities. However, neither magnitude estimations nor category ratings yielded the linear functions predicted from the Invariance Principle when plotted on log-log axes. Instead, both procedures yielded concave-upward response functions for the group data as well as for the individual data sets of the six subjects. Moreover, unlike previous reports of a nonlinear relationship, we found a linear relationship between magnitude estimations and category ratings. Rather than implying an equivalence of the underlying sensory scales, however, our results may imply subjects used a similar attention strategy for both procedures. We consider some theoretical suggestions, including an attention-band concept, for modification of a multistage stimulus-response (S-R) transformation model.     

The stimulus range effect: Evidence for top-down control of sensory intensity in audition

The influence of intensity range on the perceived magnitude of a stimulus is well documented and usually attributed to response biases. Recent studies, however, have suggested that the range effect might be sensory in origin. To test this notion, we had one set of subjects compare loudness intervals in three conditions : a broad-range condition (15 tones, 23–95 dB SPL), a soft shortrange condition (the lowest 10 tones from the broad-range condition), and a loud short-range condition (the highest 10 tones). Nonmetric scaling showed that the broad-range and loud short-range conditionshad identical loudness functions, However, the second derivative of the loudness function was larger for the soft short-range condition than fox the broad-range condition. This pattern of results is consistent with the notion of a nonlinear ampler whose gain and degree of nonlinearity are adjusted under top-down control, so as to prevent distortion and increase discriminabztity.     

Heart-rate responses of infant rats and guinea pigs to stimulus onset and offset: tests of the generality of a bidirectional effect

To test the generality, across modality and across species, of a bidirectional effect of photic stimulation in infant rats found in previous experiments, two experiments examined the effects on heart rate (HR) of onset and offset of auditory stimulation in rats and of photic stimulation in guinea pigs. Experiment 1 demonstrated a unidirectional, decelerative response in rats 17 and 21 days of age to the onset and offset of a 1-kHz tone, at both low (80 dB) and high (100 dB) intensity levels and at 14 days to the onset of the high-intensity tone. Experiment 2 demonstrated that infant guinea pigs, which unlike infant rats are precocial and not nocturnal, responded to the offset but not to the onset of light, and that this response was decelerative. These results indicated a lack of generality of the bidirectional HR effect, and were discussed in terms of the orienting/defensive reflex distinction.     

Loudness and loudness discrimination

A model is developed which holds that pure-tone intensity discrimination and suprathreshold loudness judgments are based on the same sensory representation. In this model, loudness is a power function of sound intensity. When two tones are presented sequentially, each gives rise to a loudness value along the sensory continuum. In intensity-discrimination experiments, threshold is reached when the loudness difference between the tones exceeds a criterial value. For suprathreshold presentations of tone pairs, judgments of loudness differences are based on the loudness difference between the two tones. The model is shown to accord well with data from both classes of experiments.     

Aging and auditory temporal sequencing: ordering the elements of repeating tone patterns

In a series of experiments, we examined age-related differences in adults' ability to order sequences of tones presented at various speeds and in contexts designed to promote or to impede stream segregation. In Experiment 1, 32 listeners (16 young, 16 old) were required to identify two repeating sequences that consisted of four tones (two from a high and two from a low frequency range) in different order. In Experiment 2, 32 listeners were required to judge whether the two recycled patterns from Experiment 1 were the same or different. In Experiment 3, four young and four old listeners were tested on the tasks of Experiment 2 over an extended period. In Experiment 4, 16 young and 16 old listeners were tested with sequences that were not recycled and were composed of tones drawn from a narrow frequency range. Elderly adults were less able than young adults to distinguish between tone sequences with contrasting order, regardless of the speed of presentation, the nature of the task (identification vs. same/different), the amount of practice, the frequency separation of the tones, or the presence or absence of recycling. These findings provide evidence of a temporal sequencing impairment in elderly listeners but reveal no indication of age differences in streaming processes.     

Interference effects in tone memory

Memory for a standard tone in comparison to a subsequent test tone was examined in three experiments with three intervening tones between the standard and test tones. In each trial, the intervening tones were presented from one of seven frequency range and distance from the standard tone conditions. Experiment 1 tone patterns were played at four different presentation rates, and the subjects judged whether the test was higher or lower than the standard. Memory interference effects caused by the different intervening tone conditions could be accounted for by a directional shift in the standard tone memory toward the intervening tones and by a general decrease in the standard tone memory strength with more distant intervening tones. Interference effects were smaller for the rapid presentation rates because the intervening tones formed separate "perceptual streams." Two additional experiments presented the tone patterns in a task requiring the subjects to match a continuously variable tone to their memory of the standard (Experiment 2) and a task requiring them to judge whether the standard and test tones were the "same" or "different" (Experiment 3). These experiments showed large differences in interference effects as a function of the required judgment and the subjects' musical experience.     

Does stimulus context affect loudness or only loudness judgments?

Marks (1988) reported that when equal-loudness matches were inferred from magnitude estimates of loudness for tones of two different frequencies, the matches were affected by changes in the stimulus intensity range at both frequencies. Marks interpreted these results as reflecting the operation of response biases in the subjects' estimates; that is, the effect of range was to alter subjects' judgments but not necessarily the perception of loudness itself. We investigated this effect by having subjects choose which of two tone pairs defined the larger loudness interval. By using tones of two frequencies, and varying their respective intensity ranges, we reproduced Marks' result in a procedure devoid of numerical responses. When the tones at one frequency are all soft, but the tones at the other frequency are not all soft, cross-frequency loudness matches are different from those obtained with other intensity range combinations. This suggests that stimulus range affects the perception of loudness in addition to whatever effects it may have on numerical judgments of loudness.     

Within-modality and cross-modality attentional blinks in a simple discrimination task

Following up on studies of the "attentional blink," we studied interference between successive target stimuli in visual and auditory modalities. In each experiment, stimuli were two tones and four dots, simultaneously presented for 1,800 msec. Targets were brief intensity changes in either a tone or a dot. Subjects gave unspeeded responses. In four experiments, our results showed interference between targets in the same modality, but not across modalities. We conclude that, under our experimental conditions, restrictions in concurrent target identification are largely modality specific.     

Confrontation naming impairment in dementia

In tone languages pitch variations (tones) serve to distinguish the lexical meanings of words. This study was conducted to examine the extent and nature of impairment in the perception of tones by aphasic patients who were monolingual speakers of Thai, a tone language which has five contrastive tones (mid, low, falling, high, rising). Six subjects participated in the study: two Broca aphasics, one transcortical motor aphasic, one conduction aphasic, one right brain-damaged nonaphasic, and one normal control. Three sets of stimuli (two real-speech, one synthetic-speech) were presented for identification, each set containing five Thai words minimally distinguished by tone. Results of the perception tests indicated that the performance of all four left brain-damaged aphasics differed significantly from that of the normal control, while the performance of the right brain-damaged nonaphasic did not. The normal performance of the right brain-damaged nonaphasic patient on this tone identification task suggests that deficits in the perception of tone exhibited by left brain-damaged patients can be attributed specifically to pathology in the language dominant hemisphere rather than to a general brain-damage effect. No difference in performance among the left brain-damaged patients could be attributed to a specific type of aphasic syndrome. The pattern of tonal confusions of the aphasics in comparison to that of normals suggests that their deficit is primarily quantitative rather than qualitative. Although two (mid, low) of the five tones accounted for a large percentage of the aphasics' errors, no uniform rank order of tones in terms of identifiability could be established across aphasic subjects, which suggests that their deficit is general to all five tones rather than selective to individual tones.     

汉语普通话声调T2-T4范畴化感知的老化效应

本研究考察了50~80岁说普通话的中老年人对普通话声调T2—T4的范畴化感知表现,探究影响声调范畴化感知老化的因素。采用经典范畴感知范式。结果显示,(1)中老年组所有年龄段(50~60岁、60~70岁、70~80岁)的范畴边界宽度都显著大于年轻组,但中老年组间差异不显著。(2)中老年人范畴边界宽度与记忆广度测试得分呈显著负相关,而与年龄的相关性不显著。(3)和年轻组相比,中老年组范畴内识别函数的斜率差异显著,而范畴间差异不显著。结果表明,中老年人声调感知范畴化程度下降,音系层面的加工能力发生衰退,记忆广度的衰退与声调范畴化感知老年化之间存在关联。此外,50到80岁间,年龄不会直接影响声调感知范畴化程度。     

Temporal preparation decreases perceptual latency: Evidence from a clock paradigm

A clock paradigm was employed to assess whether temporal preparation decreases the time to detect the onset of a stimulus—that is, perceptual latency. In four experiments participants watched a revolving clock hand while listening to soft or loud target tones under high or low temporal preparation. At the end of each trial, participants reported the clock hand position at the onset of the target tone. The deviation of the reported clock hand position from the actual position indexed perceptual latency. As expected, perceptual latency decreased with target tone intensity. Most importantly, however, greater temporal preparation decreased perceptual latency in all four experiments, especially for soft tones, which supports rather directly the idea that temporal preparation diminishes the duration of perceptual processing.     

Effect of masker level on infants' detection of tones in noise

In adult listeners, the signal-to-noise ratio at masked threshold remains constant with increases in masker level over a wide range of stimulus conditions. This relationship was examined in 7-month-old infants by obtaining masked thresholds for .5- and 4-kHz tones presented in four levels of continuous masking noise. Adults were also tested for comparison. Masker spectrum levels ranged from 5 to 35 dB/Hz for .5-kHz tones, and from -5 to 25 dB/Hz for 4-kHz stimuli. Thresholds were determined for stimuli of both 10 and 100 msec in duration. The results indicated that infants' performance was more adult-like for 4-kHz stimuli. Although mean thresholds for both 10- and 100-msec, 4-kHz tones were approximately 7 dB higher in infants than in adults, E/N0 at threshold remained essentially constant over the 30-dB range of maskers employed. By contrast, infants' thresholds for .5-kHz tones were exceptionally high at lower levels of the masker. Threshold E/N0 decreased significantly as masker level increased from 5 to 35 dB/Hz, and this decrease was significantly greater for 10- than for 100-msec stimuli. Temporal summation of .5-kHz tones, measured as the difference between thresholds obtained at the two signal durations, was greater for infants than for adults at low levels of the masker. However, because infants' thresholds improved more rapidly with level for 10- than for 100-msec tones, age differences in temporal summation were no longer significant when masker spectrum level was 35 dB/Hz. These results suggest that the relationship between signal-to-noise ratio at masked threshold and level of the masker is dependent on both signal frequency and duration during infancy.     

Effect of masker level on infants’ detection of tones in noise

In adult listeners, the signal-to-noise ratio at masked threshold remains constant with increases in masker level over a wide range of stimulus conditions. This relationship was examined in 7-month-old infants by obtaining masked thresholds for .5- and 4-kHz tones presented in four levels of continuous masking noise. Adults were also tested for comparison. Masker spectrum levels ranged from 5 to 35 dB/Hz for .5-kHz tones, and from ?5 to 25 dB/Hz for 4-kHz stimuli. Thresholds were determined for stimuli of both 10 and 100 msec in duration. The results indicated that infants’ performance was more adultlike for 4-kHz stimuli. Although mean thresholds for both 10- and 100-msec, 4-kHz tones were approximately 7 dB higher in infants than in adults, E/N₀ at threshold remained essentially constant over the 30-dB range of maskers employed. By contrast, infants’ thresholds for .5-kHz tones were exceptionally high at lower levels of the masker. Threshold E/N0 decreased significantly as masker level increased from 5 to 35 dB/Hz, and this decrease was significantly greater for 10- than for 100-msec stimuli. Temporal summation of .5-kHz tones, measured as the difference between thresholds obtained at the two signal durations, was greater for infants than for adults at low levels of the masker. However, because infants’ thresholds improved more rapidly with level for 10- than for 100-msec tones, age differences in temporal summation were no longer significant when masker spectrum level was 35 dB/Hz. These results suggest that the relationship between signal-to-noise ratio at masked threshold and level of the masker is dependent on both signal frequency and duration during infancy.     

The ideomotor principle and motor sequence acquisition: Tone effects facilitate movement chunking

Participants practiced short sequences of key presses; sequence length and response-effect mapping were the independent variables. Contingent, distinct key-effect relations were contrasted with either contingent but uniform or no response effects. In Experiment 1, tone effects were relevant as response-specific stimuli and also as effects. The sequence length effect for the tones group was reduced. In Experiment 2, participants were informed about the sequences to be executed and then given varying amounts of preparation time before the start signal. A reduction in the sequence length effect was observed, and initiation times and mean interresponse time (IRTs) were generally reduced in the tone group. Preparation time could compensate for some but not all of the latency reducing influence of the tone effects. The results are discussed with reference to ideomotor approaches to motor control, i.e., the notion that actions are represented in sensory format.     

Vowel quality changes produced by surrounding tone sequences

In three experiments, we examined whether energy at the same frequency as one of a vowel's harmonics in the F1 region can be captured by a preceding or following sequence of tones. The position of the /I/-/E/ phoneme boundary along an F1 continuum was used to assess the extent of capture. The first two experiments showed that a sequence of tones at 500 Hz (56-msec duration at 10/sec) can perceptually remove added energy at 500 Hz from a steady vowel (F0 = 125 Hz) that forms part of the sequence. The effect is detectable with one preceding tone, asymptotes with four, and is greater when two tones follow the vowel than when none do. Rising and falling sequences of tones (at 62.5-Hz intervals or at whole-tone intervals) differ in their effect. Falling sequences behave much like constant tones at 500 Hz but with less effect, whereas rising sequences show no evidence of removing the added tone. The second experiment replicated the first and also showed that when the vowel is embedded in a rising or a falling sequence of tones that continue after it, the following tones have no effect. The third experiment suggested that the different effects found with rising versus falling sequences are qualitatively predictable on the basis of the additive effects of their constituent tones rather than by virtue of their contour. The experiments indicated that sequences of repeating tones are much more effective at capturing a harmonic from a vowel than are sequences that follow a simple pattern. This result may reflect the operation of a principle of least commitment in auditory grouping.     

The Spectrally Dependent Monotic Component in the Decreasing-Loudness Aftereffect: Implications for Dynamic Auditory Localization

Listeners exposed to a tone increasing in intensity report an aftereffect of decreasing loudness in a steady tone heard afterward. In the present study, the spectral dependence of the monotic decreasing-loudness aftereffect (adapting and testing 1 ear) was compared with (a) the spectral dependence of the interotic decreasing-loudness aftereffect (adapting 1 ear and testing the other ear) and (b) a non-adaptation control condition. The purpose was to test the hypothesis that the decreasing-loudness aftereffect may concern the sensory processing associated with dynamic localization. The hypothesis is based on two premises: (a) dynamic localization requires monaural sensory processing, and (b) sensory processing is reflected in spectral selectivity. Hence, the hypothesis would be supported if the monotic aftereffect were more spectrally dependent and stronger than the interotic aftereffect; A. H. Reinhardt-Rutland (1998) showed that the hypothesis is supported with regard to the related increasing-loudness aftereffect. Two listeners were exposed to a 1-kHz adapting stimulus. From responses of “growing softer” or “growing louder” to test stimuli changing in intensity, nulls were calculated; test carrier frequencies ranged from 0.5 kHz to 2 kHz. Confirming the hypothesis, the monotic aftereffect peaked at around the 1-kHz test carrier frequency. In contrast, the interotic aftereffect showed little evidence of spectrally dependent peaking. Except when test and adaptation carrier frequencies differed markedly, the interotic aftereffect was smaller than the monotic aftereffect.     

The spectrally dependent monotic component in the decreasing-loudness aftereffect: implications for dynamic auditory localization

Listeners exposed to a tone increasing in intensity report an aftereffect of decreasing loudness in a steady tone heard afterward. In the present study, the spectral dependence of the monotic decreasing-loudness aftereffect (adapting and testing 1 ear) was compared with (a) the spectral dependence of the interotic decreasing-loudness aftereffect (adapting 1 ear and testing the other ear) and (b) a non-adaptation control condition. The purpose was to test the hypothesis that the decreasing-loudness aftereffect may concern the sensory processing associated with dynamic localization. The hypothesis is based on two premises: (a) dynamic localization requires monaural sensory processing, and (b) sensory processing is reflected in spectral selectivity. Hence, the hypothesis would be supported if the monotic aftereffect were more spectrally dependent and stronger than the interotic aftereffect; A. H. Reinhardt-Rutland (1998) showed that the hypothesis is supported with regard to the related increasing-loudness aftereffect. Two listeners were exposed to a 1-kHz adapting stimulus. From responses of "growing softer" or "growing louder" to test stimuli changing in intensity, nulls were calculated; test carrier frequencies ranged from 0.5 kHz to 2 kHz. Confirming the hypothesis, the monotic aftereffect peaked at around the 1-kHz test carrier frequency. In contrast, the interotic aftereffect showed little evidence of spectrally dependent peaking. Except when test and adaptation carrier frequencies differed markedly, the interotic aftereffect was smaller than the monotic aftereffect.