Noise Duration Research Articles

Effects of glide slope, noise intensity, and noise duration on the extrapolation of FM glides through noise.

Listeners are quite adept at maintaining integrated perceptual events in environments that are frequently noisy. Three experiments were conducted to assess the mechanisms by which listeners maintain continuity for upward sinusoidal glides that are interrupted by a period of broadband noise. The first two experiments used stimulus complexes consisting of three parts: prenoise glide, broadband noise interval, and postnoise glide. For a given prenoise glide and noise interval, the subject's task was to adjust the onset frequency of a same-slope postnoise glide so that, together with the prenoise glide and noise, the complex sounded as "smooth and continuous as possible." The slope of the glides (1.67, 3.33, 5, and 6.67 Bark/sec) as well as the duration (50, 200, and 350 msec) and relative level of the interrupting noise (0, -6, and -12 dB S/N) were varied. For all but the shallowest glides, subjects consistently adjusted the offset portion of the glide to frequencies lower than predicted by accurate interpolation of the prenoise portion. Curiously, for the shallowest glides, subjects consistently selected postnoise glide onset-frequency values higher than predicted by accurate extrapolation of the prenoise glide. There was no effect of noise level on subjects' adjustments in the first two experiments. The third experiment used a signal detection task to measure the phenomenal experience of continuity through the noise. Frequency glides were either present or absent during the noise for stimuli like those use in the first two experiments as well as for stimuli that had no prenoise or postnoise glides. Subjects were more likely to report the presence of glides in the noise when none occurred (false positives) when noise was shorter or of greater relative level and when glides were present adjacent to the noise.

Infant Auditory Temporal Acuity: Gap Detection

The development of auditory temporal acuity during infancy was examined in 3-, 6-, and 12-month-old infants and in adults using the gap detection paradigm. Listeners detected a series of gaps, or silent intervals, or variable duration in a broadband noise. In order to vary the acoustic frequencies available to the listener, a high-pass noise was used to mask frequencies above specified cutoffs. High-pass maskers with cutoffs of 500, 2,000, and 8,000 Hz were used. The minimum detectable gap was determined using the Observer-based Psychoacoustic Procedure. The thresholds of 3- and 6-month-olds were considerably poorer than those of the adults, although the effect of masker condition was about the same for these 3 groups. The thresholds of 12-month-olds were significantly worse than the adults when the stimulus was unmasked or when the masker cutoff frequency was 2,000 or 8,000 Hz. When the masker cutoff frequency was 500 Hz, 12-month-olds fell into 2 groups: some had gap thresholds that were about the same as 3- and 6-month-olds, while some had gap thresholds that approached those of adults. In a second experiment, a larger group of 12-month-olds were tested with a 500-Hz masker cutoff. Average performance of 12-month-olds was about the same as that of 3- and 6-month-olds in Experiment 1. Some infants attained thresholds close to those of adults. Thus, gap detection thresholds are quite poor in infants, although the similarity of the effect of frequency on performance in infants and adults suggests that the mechanisms governing temporal resolution in infants operate qualitatively like those in adults.

Infant Auditory Temporal Acuity: Gap Detection

The development of auditory temporal acuity during infancy was examined in 3-, 6-, and 12-month-old infants and in adults using the gap detection paradigm. Listeners detected a series of gaps, or silent intervals, or variable duration in a broadband noise. In order to vary the acoustic frequencies available to the listener, a high-pass noise was used to mask frequencies above specified cutoffs. High-pass maskers with cutoffs of 500, 2,000, and 8,000 Hz were used. The minimum detectable gap was determined using the Observer-based Psychoacoustic Procedure. The thresholds of 3- and 6-month-olds were considerably poorer than those of the adults, although the effect of masker condition was about the same for these 3 groups. The thresholds of 12-month-olds were significantly worse than the adults when the stimulus was unmasked or when the masker cutoff frequency was 2,000 or 8,000 Hz. When the masker cutoff frequency was 500 Hz, 12-month-olds fell into 2 groups: some had gap thresholds that were about the same as 3- and 6-month-olds, while some had gap thresholds that approached those of adults. In a second experiment, a larger group of 12-month-olds were tested with a 500-Hz masker cutoff. Average performance of 12-month-olds was about the same as that of 3- and 6-month-olds in Experiment 1. Some infants attained thresholds close to those of adults. Thus, gap detection thresholds are quite poor in infants, although the similarity of the effect of frequency on performance in infants and adults suggests that the mechanisms governing temporal resolution in infants operate qualitatively like those in adults.

Spectral, Intensive, and Temporal Factors Influencing Overshoot

Threshold was measured for a 10-msec, 4.0-kHz signal presented near the onset or in the temporal centre of a 400-msec noise masker. Overshoot, the difference (in dB) between these two thresholds, was seen only for masker bandwidths wider than a critical band. The threshold near masker onset, and hence overshoot, could be reduced by the presence of an additional noise that was presented continuously or gated on and off prior to masker onset. The spectral, intensive, and temporal properties of this effect were studied. When the additional noise was continuous and either bandpass filtered with a variable bandwidth or notch filtered with a variable notchwidth, the results indicated that energy both near and remote from the signal frequency contributed to the reduction in overshoot. The effect of this additional noise was highly dependent upon its relative level. When the additional noise was 400 msec in duration and the delay between its offset and the onset of the masker was varied, overshoot "recovered" to its maximum value within about 50 msec. Finally, as the duration of the additional noise was varied from 3 to 400 msec while the time between its offset and masker onset was fixed, the reduction in overshoot was virtually complete for durations of about 25-50 msec. The results are consistent with the notion that overshoot at least partly reflects peripheral adaptation, and that this adaptation is not restricted to the signal frequency channel but, rather, extends in both directions over several channels.

Responses of the T‐Wave Amplitude as a Function of Active and Passive Tasks and Beta‐Adrenergic Blockade

This paper presents evidence that phasic changes in T-wave amplitude vary as a function of task conditions and beta-adrenergic drugs. Three experiments were designed to test the sensitivity of T-wave amplitude to manipulations in sympathetic arousal. In the first experiment, T-wave amplitude was recorded during an active behavioral task in which 32 subjects believed that they could control the duration of an aversive white noise and during a passive behavioral task in which another 30 subjects knew that they had no control. T-wave amplitude decreased to a greater extent in the active behavior group than in the passive group. In the second experiment, 9 subjects receiving one of two beta-adrenergic blockers and 10 subjects receiving placebo completed the active task. Task-induced reductions in T-wave amplitude were systematically blocked by the beta blockers. In the third experiment, 5 subjects received placebos and 15 received one of two different beta blockers. All subjects performed a mental arithmetic task. Subjects receiving a placebo, but not those receiving beta blockade, exhibited a significant reduction in T-wave amplitude during mental arithmetic.

Development and testing of artificial low-frequency speech codes

In a new approach to the frequency-lowering of speech, artificial codes were developed for 24 consonants (C) and 15 vowels (V) for two values of lowpass cutoff frequency F (300 and 500 Hz). Each individual phoneme was coded by a unique, nonvarying acoustic signal confined to frequencies less than or equal to F. Stimuli were created through variations in spectral content, amplitude, and duration of tonal complexes or bandpass noise. For example, plosive and fricative sounds were constructed by specifying the duration and relative amplitude of bandpass noise with various center frequencies and bandwidths, while vowels were generated through variations in the spectral shape and duration of a ten-tone harmonic complex. The ability of normal-hearing listeners to identify coded Cs and Vs in fixed-context syllables was compared to their performance on single-token sets of natural speech utterances lowpass filtered to equivalent values of F. For a set of 24 consonants in C-/a/ context, asymptotic performance on coded sounds averaged 90 percent correct for F = 500 Hz and 65 percent for F = 300 Hz, compared to 75 percent and 40 percent for lowpass filtered speech. For a set of 15 vowels in /b/-V-/t/ context, asymptotic performance on coded sounds averaged 85 percent correct for F = 500 Hz and 65 percent for F = 300 Hz, compared to 85 percent and 50 percent for lowpass filtered speech. Identification of coded signals for F = 500 Hz was also examined in CV syllables where C was selected at random from the set of 24 Cs and V was selected at random from the set of 15 Vs. Asymptotic performance of roughly 67 percent correct and 71 percent correct was obtained for C and V identification, respectively. These scores are somewhat lower than those obtained in the fixed-context experiments. Finally, results were obtained concerning the effect of token variability on the identification of lowpass filtered speech. These results indicate a systematic decrease in percent-correct score as the number of tokens representing each phoneme in the identification tests increased from one to nine.

Effects of Low-Intensity Exercise and Noise Exposure on Temporary Threshold Shift

It is not known if an individual who is susceptible to temporary threshold shift (TTS) may also suffer permanent hearing loss. Risk for hearing loss is caused by the physical properties (frequency, intensity, and duration) of noise and other possible factors including physical exercise. Seventeen subjects cycled at 40% of maximum oxygen consumption (VO2 max) with and without noise administered via personal headphones. Exercising at 40% of VO2 max is considered to be low intensity. Hearing tests before and after these two exercise conditions and a noise-only condition indicated that TTS only occurred when noise was present, that is, exercise alone did not result in TTS. Therefore TTS and subsequent hearing loss (which only persisted for 24-48 h) was found to be driven by noise exposure, not low-intensity exercise.

Differential effects of controllable and uncontrollable acute stress on lymphocyte proliferation and leukocyte percentages in humans

This study examined the effects of a 30-min laboratory stressor on aspects of immune function in 24 men and whether behavioral control over the stressor moderates stress effects. The stressor consisted of mild (2.5 mA) electric shock and loud (100 dB) white noise administered in an unpredictable, intermittent fashion. During stress sessions, only half of the subjects were able to control the stressor. Subjects with control were yoked to subjects who could not control the stressor so that both groups were exposed to identical intensity and duration of noise and shock. Immunologic function was assessed across stress and nonstress conditions by measuring changes in lymphocyte proliferation to concanavalin A (Con A) and phytohemagglutinin (PHA) and by measuring changes in percentages of lymphocytes and their subpopulations, granulocytes, and monocytes. Results revealed that exposure to the uncontrollable stressor altered mood but did not affect immune function. In contrast, exposure to controllable stress did not alter mood but did result in lowered lymphocyte proliferation to Con A. Poststress percentages of monocytes were also lower in subjects exposed to the controllable stressor. Results suggest that acute stress can alter aspects of immune function in humans and underscore the importance of stressor controllability in moderating stress effects on human immunity.

Hearing acoustic details of speech. III. Discrimination of fricative duration

Listeners' ability to dicriminate the duration of the frication noise in the syllable /t∫a/ was measured. An 842‐ms token of /t∫a/ produced by a female talker was digitized at 20 kHz, output via a D/A converter and presented on each interval of a 2IFC task. On each trial, one of the intervals contained a 5–35‐ms decrement in the duration of the 183‐ms frication noise. Duration decrements were obtained by removing segments from the temporal center of the noise. Normal‐hearing listeners decided whether the first or the second interval contained the shorter‐duration frication noise. Duration discrimination was studied for frication noise presented in isolation and in syllabic context. Duration‐discrimination thresholds [P(c) = 75] were interpolated from probits fitted to 7‐point psychometric functions. On the average, thresholds in isolation were ∼14 ms or ∼8% of the duration of the frication noise. Thresholds in context were ∼32.0 ms or ∼18% of the fricative duration. Although larger than in isolation, thresholds in context are smaller than 8% of the overall syllable duration. [Work supported by OCAST Grant HSO‐005 and Presbyterian Health Foundation.]

Sharpness and amplitude envelopes of broadband noise

This paper discusses how amplitude envelope shapes, sound-pressure level, and duration of broadband noise affect sharpness and brightness. In the first experiment, sharpness, brightness, and similarity were judged for paired stimuli by 13 subjects. The stimuli consisted of broadband noise with different types of amplitude envelopes, sound-pressure levels, and duration. Experimental results were analyzed with a multidimensional scaling technique. In addition, the second experiment measuring the point of subjective equality (PSE) of sharpness was carried out for four subjects. The results of these two experiments showed large individual differences in sharpness judgment, difficulty in brightness judgment for the stimuli used in the experiments, and influence of the amplitude envelope shapes on sharpness. The individual differences observed in sharpness judgment were explained by the differences between weights given to two psychological dimensions: loudness and subjective duration. This study forms a basis for understanding sharpness of nonsteady sounds.

Effects of temporal position on the detectability of interaurally uncorrelated noise

Listeners' ability to detect an interaurally uncorrelated segment of noise within binaural broadband noise bursts was measured as a function of the temporal position of the uncorrelated noise. Psychometric functions were obtained by varying the duration of uncorrelated noise. The results indicate that detectability improves as the duration of uncorrelated noise is increased. Temporal position affected detectability only at the shortest durations of uncorrelated noise tested; a segment positioned either at the end or at the beginning of the burst is more detectable than one in the middle. This result is not easily accounted for by models of binaural processing. For example, the EC model [N. I. Durlach, J. Acoust. Soc. Am. 35, 1206–1218 (1963)] assumes that performance is determined by the power of the difference in the waveforms in the two auditory channels. Since power is computed over the total stimulus duration, it is independent of the temporal position of the uncorrelated noise. The relationship of the current findings to those for the discriminability of diotic noise stimuli will be discussed. [Work supported by AFOSR.]

Effects of a silent temporal interval on discriminability of bursts of reproducible noise

A same‐different psychophysical method was used to examine the discriminability of bursts of reproducible noise. Bursts in a pair were identical on “same” trials. On “different” trials, bursts were identical except for τ ms of independent noise located at either the beginning, middle, or end of the burst pairs. Fallon and Robinson [J. Acoust. Soc. Am. Suppl. 1 78, S46 (1985)] showed that discriminability depends on the temporal position and proportional duration of the independent noise. The present experiments examined whether a silent interval placed either immediately prior to or following the independent noise improves discriminability. Results showed that a silent interval only improved discriminability if it replaced a portion of the noise common to the pairs of bursts. In this experiment, a brief burst of common noise temporally separated from the independent noise by 90–120 ms caused a large decrement in performance. These data suggest that interactions occurring after such a long silent interval ...

Duration of frication noise required for identification of English fricatives.

Natural speech consonant-vowel (CV) syllables [( f, s, theta, s, v, z, ŏ] followed by [i, u, a]) were computer edited to include 20-70 ms of their frication noise in 10-ms steps as measured from their onset, as well as the entire frication noise. These stimuli, and the entire syllables, were presented to 12 subjects for consonant identification. Results show that the listener does not require the entire fricative-vowel syllable in order to correctly perceive a fricative. The required frication duration depends on the particular fricative, ranging from approximately 30 ms for [s, z] to 50 ms for [f, s, v], while [theta, ŏ] are identified with reasonable accuracy in only the full frication and syllable conditions. Analysis in terms of the linguistic features of voicing, place, and manner of articulation revealed that fricative identification in terms of place of articulation is much more affected by a decrease in frication duration than identification in terms of voicing and manner of articulation.

Magnetic responses of the human auditory cortex to noise/square wave transitions

We recorded evoked magnetic fields from the human auditory cortex to noise/square wave sequences. Two prominent deflections were observed: one 100 msec after the noise onset (N100m) and another 100 msec after the noise/square wave transition (N100m'). The amplitude of N100m' increased with decrease in square wave frequency from 2 kHz to 0.125 kHz and with increase in square wave duration from 4 msec to 200 msec. The latency of N100m' was on the average 23 msec longer for noise durations of 60 msec than 310 msec, whereas the amplitude of N100m' did not change. Increase in interstimulus interval from 1.1 to 8.8 sec enhanced the amplitude of N100m significantly more than that of N100m'. The small interaction between N100m and N100m' and their different recovery cycles suggest that different activation patterns underlie these two 100 msec responses at the auditory cortex.

Discrimination of duration ratios by native English and Estonian listeners

It has been suggested that Estonian has a three-way quantity distinction among disyllabic word structures in terms of the ratio of the duration of first syllable compared to the duration of the second syllable. The present study examines the ability of Estonian speakers and American English speakers to discriminate among a set of duration ratios independent of other phonetic factors such as fundamental frequency or segmental variations. Subjects were required to discriminate among pairs of noise bursts whose durations were in the ratios of 1 : 2, 2: 3, 3: 2 and 2 : 1. In half the noise sequences the combined duration of noise 1 + noise 2 was 350ms, in the other half the combined duration was 450 ms. The results obtained show that both groups of listeners clearly recognized only two contrastive patterns: 1 : 2 and 2 : 3 vs. 3 : 2 and 2 : 1. In addition, overall sequence duration had a significant effect upon duration ratio discrimination. In terms of a language group difference, the Estonian and English groups differed only in terms of responses to very different ratios (e.g. 1 : 2 vs. 2 : 1; 2 : 3 vs. 2 : 1), in particular, the Estonian group produced fewer errors. The data support a reanalysis of the three-way quantity contrast into two distinct binary decisions: one based on quantity (short–long vs. long–short disyllabic structures) and one possibly based on fundamental frequency differences.

Discrimination of duration ratios in Estonian and English

Estonian has been described as having a three‐way quantity distinction among disyllabic words based upon whether the ratio of the durations of syllable 1 to syllable 2 is approximately 2:3, 3:2, or 2:1. The present study was designed to examine the ability of listeners to discriminate among such duration ratios independent of other phonetic factors, such as fundamental frequency or segmental variations. Pairs of noise bursts (with 10 ms rise/fall times) whose durations were in the ratios of 1:2, 2:3, 3:2, and 2:1, were constructed. In half of these noise sequences the combined duration of noise 1 + noise 2 was 350 ms; in the other half the combined duration was 450 ms. Subjects were presented with two such sequences and were required to respond whether the duration ratios in the two sequences were the same or different. Equal numbers of sames and differents were randomly presented to 56 native listeners (and five trained phoneticians). Twenty‐eight listeners were native Estonians (whose data were collected in Tallinn, Estonia) and 28 listeners were native American English speakers (whose data collected in Columbus, OH). Obtained results show that both groups of listeners clearly recognized only two contrastive patterns: 1:2 and 2:3 vs 3:2 and 2:1. In addition, overall sequence duration had a significant effect upon duration ratio discriminations. These results will be discussed in light of possible language group difference, phonetic training differences, and in terms of psychoacoustic limits on the contrastive use of duration in languages.

Noise-induced hearing loss in relation to vibration-induced white finger in chain-saw workers.

From the viewpoint of the etiologies of noise-induced permanent threshold shift (NIPTS) and vibration-induced white finger (VWF), the association between VWF and hearing loss was examined among 499 chain-saw workers who underwent a compulsory health examination for vibration syndrome. They were classified by age, duration of noise and vibration exposure, and the severity of VWF. The severity of VWF was evaluated according to the following criteria: no prior history; VWF history, but symptoms had disappeared; VWF present but appearing rarely; frequent appearance of VWF (more than 20 times per winter season). In three age groups (ie, 40-49, 50-59, 60-69 years) with 5-9 years of exposure, the chainsaw workers with VWF had a significantly greater hearing loss at higher frequencies than those without VWF. However, in the 10- to 14-year exposure groups, a significant difference was not found between the VWF and non-VWF groups, except that the 50- to 59-year age groups showed a significant difference in mean age. It was suggested that interindividual differences in susceptibility to noise and vibration may be the reason for the synergistic effects of noise and vibration.

Neuromagnetic responses of the human auditory cortex to on- and offsets of noise bursts.

Cortical sources of neuromagnetic responses to noise bursts were compared in 7 healthy humans. The earliest response, P40m, peaking about 40 ms after the stimulus onset, was followed by a prominent deflection in the opposite direction at about 100 ms (N100m) and by another peak at 200 ms (P200m). A sustained field, seen near the end of the 400- to 550-ms stimuli, ended with an off-response of the same polarity as N100m. All deflections could be explained by cortical activity within the Sylvian fissure. The source of P200m was anterior to other sources of the on-response, except P40m. When noise bursts, or pauses of equal duration in a continuous noise were presented to the subject, striking similarities were found between the 100-ms deflections of the on- and off-responses: both peaked at about the same latency; their estimated sources were closed to each other in the supratemporal plane and their amplitudes depended in a similar way on the interstimulus interval (1.1-8.8 s). However, only the on-response was preceded by P40m, suggesting that P40m and N100m are not causally linked. N100m seems to reflect cortical activity related to any abrupt change in the auditory environment.

EVALUATION OF FREQUENT AIRCRAFT NOISE IN FAR DISTANCE

Large airports have become to be built far in the distance of cities in Japan. In such cases, the noise duration increases because of the increases of aircraft altitude in residual areas although the noise level is reduced. Therefore it possibly provides some problems to evaluate the aircraft noise independently of environmental noise when the frequency of flight is large.The purpose of this study is to find the way to evaluate the effect of aircraft noise on the environmental noise level considering the flight frequency on the basis of quantitative relationship between the noisiness and loudness of environmental noise clarified as well as that of aircraft noise in the distance.

Altered acoustic cue discrimination in broca's and conduction aphasics

The present investigation explored the acoustic cue discrimination abilities of eight Broca's and four conduction aphasic patients and nine normal controls. A word-discrimination test was used to assess the subjects' ability to discriminate selected acoustic cues for distinctive features of phonemes. The words differed from one another by a selected minimal feature, such as stop-gap duration, duration of fricative noise, direction and extent of final format transition, or relative location of friction noise in the spectrum. Results indicated that performance for normal and aphasic subjects was poorer for altered temporal subtest items than for altered spectral subtest items. Within the spectral subtest, fewer Broca's aphasics than conduction aphasics passed the items, while 90% of the normals passed. Within the temporal subtest, fewer conduction aphasics than Broca's aphasics passed the items, while 75% of the normal subjects passed this subtest. The results support previous research suggesting that deficiencies in auditory processing of selected acoustic cues are not limited to Wernicke's aphasic individuals but may be found to a varying degree in several aphasic groups.