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PubMed2005

Detection of high-frequency spectral notches as a function of level.

High-frequency spectral notches are important cues for sound localization. Our ability to detect them must depend on their representation as auditory nerve (AN) rate profiles. Because of the low threshold and the narrow dynamic range of most AN fibers, these rate profiles deteriorate at high levels. The system may compensate by using onset rate profiles whose dynamic range is wider, or by using low-spontaneous-rate fibers, whose threshold is higher. To test these hypotheses, the threshold notch depth necessary to discriminate between a flat spectrum broadband noise and a similar noise with a spectral notch centered at 8 kHz was measured at levels from 32 to 100 dB SPL. The importance of the onset rate-profile representation of the notch was estimated by varying the stimulus duration and its rise time. For a large proportion of listeners, threshold notch depth varied nonmonotonically with level, increasing for levels up to 70-80 dB SPL and decreasing thereafter. The nonmonotonic aspect of the function was independent of notch bandwidth and stimulus duration. Thresholds were independent of stimulus rise time but increased for the shorter noise bursts. Results are discussed in terms of the ability of the AN to convey spectral notch information at different levels.

Acoustic Stimulation↗
PubMed2006

Autocorrelation in meter induction: the role of accent structure.

The performance of autocorrelation-based meter induction was tested with two large collections of folk melodies, consisting of approximately 13 000 melodies for which the correct meters were available. The performance was measured by the proportion of melodies whose meter was correctly classified by a discriminant function. Furthermore, it was examined whether including different melodic accent types would improve the classification performance. By determining the components of the autocorrelation functions that were significant in the classification it was found that periodicity in note onset locations was the most important cue for the determination of meter. Of the melodic accents included, Thomassen's melodic accent was found to provide the most reliable cues for the determination of meter. The discriminant function analyses suggested that periodicities longer than one measure may provide cues for meter determination that are more reliable than shorter periodicities. Overall, the method predicted notated meter with an accuracy reaching 96% for binary classification and 75% for classification into nine categories of meter.

Auditory Perception↗
PubMed1983

Psychophysical measures of two-tone suppression and distortion products (2f1-f2) and (f2-f1).

Psychophysical two-tone suppression and the growth of the (2f1-f2) and (f2-f1) distortion products were measured in four normal-hearing young adults using a forward-masking paradigm. The stimulus parameters investigated were: (1) f1 = 750 and 3000 Hz; (2) f2/f1 = 1.11, 1.26, and 1.41; (3) L1 = 50, 65, 80, and 90 dB SPL; and (4) L2 - L1 varied from -20 to +20 dB in 10-dB increments. It appears that the p-law class of nonlinearity, which maintains that suppression and growth functions for the distortion products are directly related, is not supported by the data. Of existing models of aural nonlinearity, Goldstein's [J. Acoust. Soc. Am. 41, 458-479 (1967)] normalized power series appears to provide the most accurate description of the data, especially when modifications brought about by suppression are incorporated into the model.

Adult↗
PubMed1983

Gap detection as a function of frequency, bandwidth, and level.

The threshold for detection of a temporal gap in a noiseband was measured. A notched noise masker was used to restrict listening to a limited spectral region. Threshold was measured as a function of center frequency, bandwidth, and level. For a signal bandwidth of one-half the center frequency, the gap threshold decreased from 22.5 ms for a center frequency of 0.2 kHz to 3.2 ms at 8.0 kHz: a wideband condition provided an estimate of 2.3 ms, a value in agreement with previously published estimates. Bandwidth manipulation showed that the variation with frequency was not due to changes in absolute bandwidth alone. The effect of changes in level was determined at three frequencies, 0.4, 1.0, and 6.5 kHz, using a signal bandwidth of half the center frequency. At all frequencies gap threshold decreased as the signal spectrum level was raised from 10 to 25 dB, but a further increase to 40 dB showed no additional improvement. At frequencies up to about 1.0 kHz, the variation of gap threshold with frequency matches well the reciprocal of the bandwidth of the auditory filter, as determined from masking experiments using a notched-noise masker. This suggests that the temporal response of the auditory filter may limit gap detection at low frequencies.

Auditory Perception↗
PubMed1983

Intensity discrimination as a function of level and frequency and its relation to high-frequency hearing.

This paper examines how intensity discrimination depends on the test frequency, the level, and the subjects's high-frequency hearing. Three experiments were performed. In the first experiment, intensity discrimination of pulsed tones was measured as a function of level at 1 and 14 kHz in five listeners. Results show less deviation from Weber's law at 14 kHz than at 1 kHz. In the second experiment, intensity discrimination was measured for a 1-kHz tone at 90-dB SPL as a function of the cutoff frequency of a high-pass masking noise in two listeners. Results show that the audibility of very high frequencies is important for frequency discrimination at 1 kHz. The DL increased by a factor between 1.5 and 2.0 as the cutoff frequency of the noise was lowered from 19 to 6 kHz. In the third experiment, thresholds from 6 to 20 kHz and intensity discrimination for a 1-kHz tone was measured in 12 listeners. Results show that the DLs at 80-dB SPL are correlated with the ability to hear very high frequencies. Results of all three experiments are consistent with the multiband version of the excitation-pattern model for intensity discrimination [Florentine and Buus, J. Acoust. Soc. Am. 70, 1646-1654 (1981)].

Adult↗
PubMed1987

Distribution of auditory-filter bandwidths at 2 kHz in young normal listeners.

Auditory-filter shapes at 2 kHz were estimated for 95 young normally hearing subjects using a notched-noise masker with spectrum level of 45 dB. Excluding two subjects with a recent history of noise exposure, the equivalent rectangular bandwidths (ERBs) of the filters were approximately normally distributed but the distribution had a slight positive skew. The mean ERB was 308 Hz and the standard deviation was 32 Hz. The two noise-exposed subjects had ERBs of 404 and 497 Hz.

Acoustic Stimulation↗
PubMed1989

The effect of varying the amplitude-frequency response on the masked speech-reception threshold of sentences for hearing-impaired listeners.

In an evaluation of frequency-dependent automatic gain-control systems in hearing aids, the effect of varying the amplitude-frequency response on the speech-reception threshold (SRT) for sentences in noise is studied for 20 hearing-impaired listeners. The noise has a spectrum identical to the long-term average spectrum of the sentences. Speech and noise are shaped by the same amplitude-frequency response; their spectra are varied relative to the bisector of the individual's dynamic range. In four experimental conditions, the effect of a steady-state amplitude-frequency response is studied. Steepening the negative spectral slope of speech and noise appears to cause an increase of masked SRT, possibly due to increased effect of upward spread of masking. The effect of a single transition of the amplitude-frequency response between 10 and -10 dB/oct halfway through the sentence seems to be related to the effect for the fixed -10-dB/oct condition. Two transition times are tested. For a transition time of 0.25 s, the SRT is only a little higher than for 1 s. The results suggest that the amplitude-frequency response may be varied in time without having a detrimental effect on the masked SRT of sentences for hearing-impaired listeners as long as strongly negatively sloping spectra are avoided.

Adult↗
PubMed1990

Neural responses to auditory temporal patterns.

Sets of regularly repeating auditory stimuli elicit unique perceptions; listeners are able to identify specific temporal patterns. Some temporal patterns are unambiguous (only one pattern can be perceived), while others are ambiguous (numerous patterns can be detected). While the psychophysical properties of such percepts have been well studied, little is known about the underlying neurological bases of temporal pattern perception. In this experiment, the role of adaptation in temporal pattern perception is examined by studying neural responses in four cats to a temporal pattern that is perceptually unambiguous and one that is perceptually ambiguous. Measurements were made of the whole-nerve action potential, the auditory brainstem response, and potentials from the surface of the primary auditory cortex. The adaptation patterns corresponded with the perceptual organization of temporal patterns in humans at all levels of the nervous system studied.

Animals↗
PubMed1991

The influence of systematic primary-tone level variation L2-L1 on the acoustic distortion product emission 2f1-f2 in normal human ears.

The purpose of the present study was to determine the effect of primary-tone level variation, L2--L1, on the amplitude of distortion-product otoacoustic emissions (DPOAEs). The DPOAE at the frequency 2f1--f2 (f2 greater than f1) was measured in 20 ears of ten normally hearing subjects. Acoustic distortion products were generated by primaries f1 and f2 with geometric mean frequencies of 1, 2, and 4 kHz. The f2/f1 ratios were 1.25 (1 kHz), 1.23 (2 kHz), and 1.21 (4 kHz). The primary-tone level L1 was kept constant at either 65 or 75 dB SPL while the second primary-tone level L2 was varied between 20 and 90 dB SPL in 5-dB steps. The level differences L2--L1 generating maximal DPOAE amplitudes depended on L1 and on the geometric mean frequency of f1 and f2. There were large interindividual differences. Overall, the L2--L1 evoking maximal mean DPOAE amplitudes was --10 dB for geometric mean frequencies of 1 and 2 kHz with both L1 = 65 dB SPL and L1 = 75 dB SPL. For 4 kHz, L2-L1 was --5 dB with L1 = 65 dB SPL and 0 dB with L1 = 75 dB SPL. The mean slopes of the DPOAE growth functions in the initial linearly increasing portions were steeper at higher stimulus frequencies, increasing from 0.52 at 1 kHz to 0.72 at 4 kHz for L1 = 65 dB SPL and from 0.48 at 1 kHz to 0.72 at 4 kHz for L1 = 75 dB SPL.

Adult↗
PubMed1991

The role of intermittence in PTS.

Exposure of chinchillas to noise that is continuous results in auditory damage that is a function of the total energy of the exposure, provided that a critical exposure is not exceeded. Breaking a continuous exposure into 45 exposure periods given once a day Monday through Friday for 9 weeks (an interrupted exposure) is shown to result in a slight reduction in damage, but breaking each of the 45 daily exposures into short noise bursts presented at regular intervals (interrupted and intermittent exposures) reduces the damage more significantly. The shorter the noise bursts, the greater will be the reduction in damage. Too few data are available to establish a principle that will predict correctly the amount of reduction afforded by a particular temporal pattern; while the "equal energy" principle predicts no reduction at all, the "mean level" principle derived from studies of temporary threshold shifts (e.g., a noise at 80 dB half the time and at 100 dB half the time has a mean level of 90 dB and will have the same effect as a continuous 90-dB noise) predicts too much reduction.

Animals↗
PubMed1992

Evidence for two discrete sources of 2f1-f2 distortion-product otoacoustic emission in rabbit: I. Differential dependence on stimulus parameters.

The results of studies of the physiological vulnerability of distortion-product otoacoustic emissions (DPOAEs) suggest that the DPOAE at 2f1-f2 in vertebrate ears is generated by more than one source. The principal aims of the present study were to provide independent evidence for the existence of more than one DPOAE source, and to determine the contributions of each to the ear-canal 2f1-f2 signal. To accomplish these aims, specific stimulus parameters were separately and systematically varied to provide detailed parametric information regarding 2f1-f2 DPOAE amplitude and phase in normal ears of awake rabbits. The findings indicate that two discrete sources, demonstrating differential dependence on stimulus parameters, dominate the generation of the 2f1-f2 DPOAE. One source of distortion is dominant above 60-70 dB SPL at moderate primary-frequency separations, and at all stimulus levels when the primary tones are closely spaced. The other source is dominant below 60-70 dB SPL at moderate primary-frequency separations, and may be dominant at all stimulus levels when the primary tones are widely separated in frequency. The results suggest that by varying stimulus parameters, it may be possible to independently study the two generator mechanisms.

Animals↗
PubMed1992

Frequency dependence of binaural performance in listeners with impaired binaural hearing.

Binaural performance was measured as a function of stimulus frequency for four impaired listeners, each with bilaterally symmetric audiograms. The subjects had various degrees and configurations of audiometric losses: two had high-frequency, sensorineural losses; one had a flat sensorineural loss; and one had multiple sclerosis with normal audiometric thresholds. Just noticeable differences (jnd's) in interaural time, interaural intensity, and interaural correlation as well as detection thresholds for NoSo and NoS pi conditions were obtained for narrow-band noise stimuli at octave frequencies from 250-4000 Hz. Performance of the impaired listeners was generally poorer than that of normal-hearing listeners, although it was comparable to normal in a few instances. The patterns of binaural performance showed no apparent relation to the audiometric patterns; even the two subjects with similar degree and configuration of hearing loss have very different binaural performance, both in the level and frequency dependence of their performance. The frequency dependence of performance on individual tests is irregular enough that one cannot confidently interpolate between octaves. In addition, it appears that no subset of the measurements is adequate to characterize the performance in the rest of the measurements with the exception that, within limits, interaural correlation discrimination and NoS pi detection performance are related.

Acoustic Stimulation↗
PubMed1992

The effects of notched noise on intensity discrimination under forward masking.

Zeng et al. [Hear. Res. 55, 223-230 (1991)] reported that at moderate levels there is an increase in the intensity jnd for 25-ms sinusoidal pedestals presented 100 ms after an intense narrow-band noise. They suggested that this effect is related to the finding that low spontaneous rate (SR) auditory-nerve neurons take a considerable time to recover from adaptation [E. M. Relkin and J. R. Doucet, Hear. Res. 55, 215-222 (1991)]: 100 ms after the noise, the low-SR neurons still have elevated thresholds. Therefore, the intensity of a pedestal falling between the saturation level of the high-SR neurons and the elevated threshold of the low-SR neurons will be poorly represented in neutral firing rates, and the jnd will be high. A problem with this interpretation is that subjects may listen "off frequency." Theoretically, it should always be possible to choose a frequency channel for which the pedestal level is within the dynamic range of the high-SR neurons. In the present study, the experiment of Zeng et al. was replicated but with the pedestal presented in the temporal center of a notched noise to prevent off-frequency listening. Surprisingly, the notched noise substantially decreased the jnd at mid levels, removing or severely reducing the mid-level jnd elevation. This was true for pedestal frequencies of 1 and 6 kHz. It was also found that even if the notched noise was terminated before pedestal onset the jnd elevation was reduced. This suggests that the effect of the notched noise is not due to suppression.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Effects of forward masking on intensity discrimination, frequency discrimination, and the detection of tones in noise.

A series of experiments investigated the deterioration in intensity discrimination at intermediate levels caused by preceding the brief sinusoidal stimuli by an intense narrow-band noise [Zeng et al., Hear. Res. 55, 223-230 (1991)]. Experiment 1 showed that this deterioration acted in a roughly additive manner with the previously reported midlevel deterioration for the intensity discrimination of brief 6500-Hz tones in quiet. The experiment also showed that a smaller, although still substantial, deterioration occurred for the detection of brief tones in bursts of synchronous noise. In experiment 2, the masker could occur either before the signal (louder tone) or standard (softer tone), the choice being selected at random on a trial-by-trial basis, and with the Weber fraction tracked for each condition separately using two interleaved, adaptive procedures. Weber fractions were lower when the masker preceded the signal than when it preceded the standard, arguing against a major role for adaptation in causing the midlevel deterioration. Instead, it is suggested that the deterioration shared a common mechanism with the phenomenon of "loudness enhancement" [R. J. Irwin and J. J. Zwislocki, Percept. Psychophys. 10, 189-192 (1971); Galambos et al., J. Acoust. Soc. Am. 52, 1127-1130 (1972)]. The third experiment showed that Weber fractions did not depend greatly on whether the forward masker occurred only in interval one or only in interval two of a two-interval trial. A fourth experiment investigated the effect of a forward masker on frequency difference limens (DLs). When the masker was presented in both intervals of each trial, there was only a moderate increase in frequency DLs which, in contrast to the elevation in Weber fractions for intensity discrimination, was independent of signal level. Presenting the masker before only the lower frequency tone of a pair to be discriminated usually yielded lower DLs than presenting it only before the higher frequency tone, but this effect was less consistent than for intensity discrimination. The results of all experiments are discussed with respect to the various ways in which an intense narrow-band masker can affect the perception of subsequent brief sounds.

Audiometry↗
PubMed1997

Discrimination of changes in the spectral shape of noise bands.

Discrimination experiments were performed for a change in the spectral shape of noise bands. The subject's task was to discriminate noise bands with a positive spectral slope from those with a negative spectral slope. Thresholds were measured at several bandwidths and center frequencies, as well as for several noise samples. Experiments were performed while roving the overall intensity. At a fixed center frequency of 1 kHz, sensitivity was best for bandwidths of 3-6 semitones (ST). At larger bandwidths, thresholds increased only slowly. At a fixed bandwidth of 1 ST, threshold hardly changed as a function of the center frequency. At a fixed bandwidth of 58 Hz, threshold was lowest near 500-1000 Hz. Model calculations show that the EWAIF model [Feth, Percept. Psychophys. 15, 375-378 (1974)] can account for the present results if the signal's bandwidth does not exceed 1 ST. The IWAIF model [Anantharaman et al., J. Acoust. Soc. Am. 94, 723-729 (1993)] can account for the present results only if the signal's bandwidth is smaller than 1 ST but larger than about 25 Hz. Results obtained with broadband signals could be described only qualitatively with the multichannel model [Durlach et al., J. Acoust. Soc. Am. 80, 63-72 (1986)]. Then, the model needs the assumption that either the output of the different frequency bands cannot be optimally combined, or that only two bands are used in the discrimination process. The present results are compared with those obtained with two-tone complexes measured under identical conditions [Versfeld and Houtsma, J. Acoust. Soc. Am. 98, 807-816 (1995)].

Auditory Perception↗