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Journal of the Acoustical Society of America

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Nov 1999

Volume 106, Issue 5, pp. 2321-L52

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Quantifying the distortion products generated by amplitude-modulated noise

Lutz Wiegrebe and Roy D. Patterson

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2709-2718 (1999); (10 pages) | Cited 12 times

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When sinusoidal amplitude modulation (SAM) is applied to noise or tone carriers, the stimuli can generate audible distortion products in the region of the modulation frequency. As a result, when bandpass-filtered SAM noise is used to investigate temporal processing, a band of unmodulated noise is typically positioned at the modulation frequency to mask any distortion products. This study was designed to investigate the distortion products for bandpass noise carriers, and so reduce ambiguity about the form of this distortion and its role in perception. The distortion consists of two distortion-noise bands and a distortion tone at the modulation frequency. In the first two experiments, the level and phase of the distortion tone are measured using two different experimental paradigms. In the third experiment, modulation-frequency difference limens are measured for filtered SAM noise and it is shown that performance deteriorates markedly when the distortion tone is canceled. In a fourth experiment, masked threshold is measured at low frequencies for bands of high-frequency, unmodulated noise with the same levels and spectra as the SAM noises in the earlier experiments. The results confirm that unmodulated noise also produces quadratic distortion which may explain some aspects of earlier reports on remote masking. © 1999 Acoustical Society of America.
Show PACS
43.66.Ba Models and theories of auditory processes
43.66.Dc Masking
43.66.Hg Pitch
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Spectro-temporal modulation transfer functions and speech intelligibility

Taishih Chi, Yujie Gao, Matthew C. Guyton, Powen Ru, and Shihab Shamma

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2719-2732 (1999); (14 pages) | Cited 22 times

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Detection thresholds for spectral and temporal modulations are measured using broadband spectra with sinusoidally rippled profiles that drift up or down the log-frequency axis at constant velocities. Spectro-temporal modulation transfer functions (MTFs) are derived as a function of ripple peak density (Ω cycles/octave) and drifting velocity (ω Hz). The MTFs exhibit a low-pass function with respect to both dimensions, with 50% bandwidths of about 16 Hz and 2 cycles/octave. The data replicate (as special cases) previously measured purely temporal MTFs (Ω=0) [Viemeister, J. Acoust. Soc. Am. 66, 1364–1380 (1979)] and purely spectral MTFs (ω=0) [Green, in Auditory Frequency Selectivity (Plenum, Cambridge, 1986), pp. 351–359]. A computational auditory model is presented that exhibits spectro-temporal MTFs consistent with the salient trends in the data. The model is used to demonstrate the potential relevance of these MTFs to the assessment of speech intelligibility in noise and reverberant conditions. © 1999 Acoustical Society of America.
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43.66.Ba Models and theories of auditory processes
43.71.Gv Measures of speech perception (intelligibility and quality)

Within-channel cues in comodulation masking release (CMR): Experiments and model predictions using a modulation-filterbank model

Jesko L. Verhey, Torsten Dau, and Birger Kollmeier

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2733-2745 (1999); (13 pages) | Cited 25 times

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Experiments and model calculations were performed to study the influence of within-channel cues versus across-channel cues in comodulation masking release (CMR). A class of CMR experiments is considered that are characterized by a single (unmodulated or modulated) bandpass noise masker with variable bandwidth centered at the signal frequency. A modulation-filterbank model suggested by Dau et al. [J. Acoust. Soc. Am. 102, 2892–2905 (1997)] was employed to quantitatively predict the experimental data. Effects of varying masker bandwidth, center frequency, modulator bandwidth, modulator type, and signal duration on CMR were examined. In addition, the effect of band limiting the noise before or after modulation was shown to influence the CMR in the same way as a systematic variation of the modulation depth. It is demonstrated that a single-channel analysis, which analyzes only the information from one peripheral channel, quantitatively accounts for the CMR in most cases, indicating that an across-channel process is generally not necessary for simulating results from this class of CMR experiments. True across-channel processes may be found in another class of CMR experiments. © 1999 Acoustical Society of America.  
Show PACS
43.66.Ba Models and theories of auditory processes
43.66.Dc Masking

Evidence against an effect of grouping by spectral regularity on the perception of virtual pitch

Valter Ciocca

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2746-2751 (1999); (6 pages) | Cited 3 times

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Two experiments investigated the role of the regularity of the frequency spacing of harmonics, as a separate factor from harmonicity, on the perception of the virtual pitch of a harmonic series. The first experiment compared the shifts produced by mistuning the 3rd, 4th, and 5th harmonics in the pitch of two harmonic series: the odd-H and the all-H tones. The odd-H tone contained odd harmonics 1 to 11, plus the 4th harmonic; the all-H tone contained harmonics 1 to 12. Both tones had a fundamental frequency of 155 Hz. Pitch shifts produced by mistuning the 3rd harmonic, but not the 4th and 5th harmonics, were found to be significantly larger for the odd-H tone than for the all-H tone. This finding was consistent with the idea that grouping by spectral regularity affects pitch perception since an odd harmonic made a larger contribution than an adjacent even harmonic to the pitch of the odd-H tone. However, an alternative explanation was that the 3rd mistuned harmonic produced larger pitch shifts within the odd-H tone than the 4th mistuned harmonic because of differences in the partial masking of these harmonics by adjacent harmonics. The second experiment tested these explanations by measuring pitch shifts for a modified all-H tone in which each mistuned odd harmonic was tested in the presence of the 4th harmonic, but in the absence of its other even-numbered neighbor. The results showed that, for all mistuned harmonics, pitch shifts for the modified all-H tone were not significantly different from those for the odd-H tone. These findings suggest that the harmonic relations among frequency components, rather than the regularity of their frequency spacing, is the primary factor for the perception of the virtual pitch of complex sounds. © 1999 Acoustical Society of America.
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43.66.Ba Models and theories of auditory processes
43.66.Hg Pitch

Intrinsic envelope fluctuations and modulation-detection thresholds for narrow-band noise carriers

Torsten Dau, Jesko Verhey, and Armin Kohlrausch

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2752-2760 (1999); (9 pages) | Cited 33 times

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A model is presented which calculates the intrinsic envelope power of a bandpass noise carrier within the passband of a hypothetical modulation filter tuned to a specific modulation frequency. Model predictions are compared to experimentally obtained amplitude modulation (AM) detection thresholds. In experiment 1, thresholds for modulation rates of 5, 25, and 100 Hz imposed on a bandpass Gaussian noise carrier with a fixed upper cutoff frequency of 6 kHz and a bandwidth in the range from 1 to 6000 Hz were obtained. In experiment 2, three noises with different spectra of the intrinsic fluctuations served as the carrier: Gaussian noise, multiplied noise, and low-noise noise. In each case, the carrier was spectrally centered at 5 kHz and had a bandwidth of 50 Hz. The AM detection thresholds were obtained for modulation frequencies of 10, 20, 30, 50, 70, and 100 Hz. The intrinsic envelope power of the carrier at the output of the modulation filter tuned to the signal modulation frequency appears to provide a good estimate for AM detection threshold. The results are compared with predictions on the basis of the more complex auditory processing model by Dau et al. [J. Acoust. Soc. Am. 99, 3615–3622 (1997)]. © 1999 Acoustical Society of America.
Show PACS
43.66.Ba Models and theories of auditory processes
43.66.Dc Masking
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Inter-relationship between different psychoacoustic measures assumed to be related to the cochlear active mechanism

Brian C. J. Moore, Deborah A. Vickers, Christopher J. Plack, and Andrew J. Oxenham

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2761-2778 (1999); (18 pages) | Cited 33 times

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The active mechanism in the cochlea is thought to depend on the integrity of the outer hair cells (OHCs). Cochlear hearing loss is usually associated with damage to both inner hair cells (IHCs) and OHCs, with the latter resulting in a reduction in or complete loss of the function of the active mechanism. It is believed that the active mechanism contributes to the sharpness of tuning on the basilar membrane (BM) and is also responsible for compressive input–output functions on the BM. Hence, one would expect a close relationship between measures of sharpness of tuning and measures of compression. This idea was tested by comparing three different measures of the status of the active mechanism, at center frequencies of 2, 4, and 6 kHz, using subjects with normal hearing, with unilateral or highly asymmetric cochlear hearing loss, and with bilateral loss. The first measure, HLOHC, was an indirect measure of the amount of the hearing loss attributable to OHC damage; this was based on loudness matches between the two ears of subjects with unilateral hearing loss and was derived using a loudness model. The second measure was the equivalent rectangular bandwidth (ERB) of the auditory filter, which was estimated using the notched-noise method. The third measure was based on the slopes of growth-of-masking functions obtained in forward masking. The ratio of slopes for a masker centered well below the signal frequency and a masker centered at the signal frequency gives a measure of BM compression at the place corresponding to the signal frequency; a ratio close to 1 indicates little or no compression, while ratios less than 1 indicate that compression is occurring at the signal place. Generally, the results showed the expected pattern. The ERB tended to increase with increasing HLOHC. The ratio of the forward-masking slopes increased from about 0.3 to about 1 as HLOHC increased from 0 to 55 dB. The ratio of the slopes was highly correlated with the ERB (r = 0.92), indicating that the sharpness of the auditory filter decreases as the compression on the BM decreases. © 1999 Acoustical Society of America.
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43.66.Dc Masking
43.66.Cb Loudness, absolute threshold
43.66.Sr Deafness, audiometry, aging effects

Different auditory filter bandwidth estimates based on profile analysis, notched noise, and hybrid tasks

Jennifer J. Lentz, Virginia M. Richards, and Matthew R. Matiasek

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2779-2792 (1999); (14 pages) | Cited 5 times

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Auditory filter bandwidths were estimated in three experiments. The first experiment was a profile-analysis experiment. The stimuli were composed of sinusoidal components ranging in frequency from 200 to 5000 Hz. The standard stimulus was the sum of equal-amplitude tones, and the signal stimulus had a power spectrum that varied up–down…up–down. The number of components ranged from four to 60. Interval-by-interval level randomization prevented the change in level of a single component from reliably indicating the change from standard to signal. The second experiment was a notched-noise experiment in which the 1000-Hz tone to be detected was added to a noise with a notch arithmetically centered at 1000 Hz. Detection thresholds were estimated both in the presence of and in the absence of level randomization. In the third, hybrid, experiment a 1000-Hz tone was to be detected, and the masker was composed of equal-amplitude sinusoidal components ranging in frequency from 200 to 5000 Hz. For this experiment, thresholds were estimated both in the presence and absence of level variation. For both the notched-noise and hybrid experiments, only modest effects of level randomization were obtained. A variant of Durlach et al.’s channel model [“Towards a model for discrimination of broadband signals,” J. Acoust. Soc. Am. 80, 63–72 (1986)] was used to estimate auditory filter bandwidths for all three experiments. When a two-parameter roex(p,r) filter weighting function was used to fit the data, bandwidth estimates were approximately two to three times as large for the two detection tasks than for the profile-analysis task. © 1999 Acoustical Society of America.
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43.66.Dc Masking
43.66.Ba Models and theories of auditory processes

Age differences in backward masking

Sara Elizabeth Gehr and Mitchell S. Sommers

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2793-2799 (1999); (7 pages) | Cited 2 times

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The present study was designed to assess the effects of age on the time course of backward masking. In experiment 1, thresholds for detecting a 10-ms, 500-Hz sinusoidal signal were measured as a function of the temporal separation between the signal and a 50-ms broadband masker. Subjects were younger (18–24) and older (over age 65) adults with normal hearing (thresholds less than 20 dB HL) for frequencies of 4 kHz and below. Younger subjects exhibited less overall masking and steeper recovery functions than did the older adults. Masked thresholds for younger participants approached unmasked thresholds for signal-masker delays greater than 6–8 ms. In contrast, older adults exhibited significant masking even at the longest delay tested (20 ms). In experiment 2, signal duration was decreased to 5 ms for a separate group of younger adults. Although overall thresholds were elevated for the shorter signal duration, the slope of the backward masking recovery function was not different from that observed for younger adults in experiment 1. The results suggest that age, independent of hearing loss, affects the temporal course of backward masking. © 1999 Acoustical Society of America.
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43.66.Dc Masking

Ripple depth and density resolution of rippled noise

A. Ya. Supin, V. V. Popov, O. N. Milekhina, and M. B. Tarakanov

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2800-2804 (1999); (5 pages) | Cited 6 times

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Depth resolution of spectral ripples was measured in normal humans using a phase-reversal test. The principle of the test was to find the lowest ripple depth at which an interchange of peak and trough position (the phase reversal) in the rippled spectrum is detectable. Using this test, ripple-depth thresholds were measured as a function of ripple density of octave-band rippled noise at center frequencies from 0.5 to 8 kHz. The ripple-depth threshold in the power domain was around 0.2 at low ripple densities of 4–5 relative units (center-frequency-to-ripple-spacing ratio) or 3–3.5 ripples/oct. The threshold increased with the ripple density increase. It reached the highest possible level of 1.0 at ripple density from 7.5 relative units at 0.5 kHz center frequency to 14.3 relative units at 8 kHz (5.2 to 10.0 ripple/oct, respectively). The interrelation between the ripple depth threshold and ripple density can be satisfactorily described by transfer of the signal by frequency-tuned auditory filters. © 1999 Acoustical Society of America.  
Show PACS
43.66.Fe Discrimination: intensity and frequency
43.66.Jh Timbre, timbre in musical acoustics

Memory for pitch versus memory for loudness

Sylvain Clément, Laurent Demany, and Catherine Semal

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2805-2811 (1999); (7 pages) | Cited 6 times

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The decays of pitch traces and loudness traces in short-term auditory memory were compared in forced-choice discrimination experiments. The two stimuli presented on each trial were separated by a variable delay (D); they consisted of pure tones, series of resolved harmonics, or series of unresolved harmonics mixed with lowpass noise. A roving procedure was employed in order to minimize the influence of context coding. During an initial phase of each experiment, frequency and intensity discrimination thresholds [P(C) = 0.80] were measured with an adaptive staircase method while D was fixed at 0.5 s. The corresponding physical differences (in cents or dB) were then constantly presented at four values of D: 0.5, 2, 5, and 10 s. In the case of intensity discrimination, performance (d′) markedly decreased when D increased from 0.5 to 2 s, but was not further reduced when D was longer. In the case of frequency discrimination, the decline of performance as a function of D was significantly less abrupt. This divergence suggests that pitch and loudness are processed in separate modules of auditory memory. © 1999 Acoustical Society of America.
Show PACS
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
43.66.Fe Discrimination: intensity and frequency
43.66.Hg Pitch
43.66.Cb Loudness, absolute threshold

Identification and localization of sound sources in the median sagittal plane

Brad Rakerd, William M. Hartmann, and Timothy L. McCaskey

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2812-2820 (1999); (9 pages) | Cited 4 times

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The ability of human listeners to identify broadband noises differing in spectral structure was studied for multiple sound-source locations in the median sagittal plane. The purpose of the study was to understand how sound identification is affected by spectral variations caused by directionally dependent head-related transfer functions. It was found that listeners could accurately identify noises with different spectral peaks and valleys when the source location was fixed. Listeners could also identify noises when the source location was roved in the median sagittal plane when the relevant spectral features were at low frequency. Listeners failed to identify noises with roved location when the spectral structure was at high frequency, presumably because the spectral structure was confused with the spectral variations caused by different locations. Parallel experiments on sound localization showed that listeners can localize noises that they cannot identify. The combination of identification and localization experiments leads to the conclusion that listeners cannot compensate for directionally dependent filtering by their own heads when they try to identify sounds. © 1999 Acoustical Society of America.
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43.66.Qp Localization of sound sources
43.66.Jh Timbre, timbre in musical acoustics

Variations in the feedback of hearing aids

Johan Hellgren, Thomas Lunner, and Stig Arlinger

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2821-2833 (1999); (13 pages) | Cited 6 times

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Variations in the loop response of hearing aids caused by jaw movements, variations in acoustics outside the ear, and variations of vent size have been identified. Behind The Ear (BTE) and In The Ear Canal (ITEC) hearing aids were considered. The largest variations among the variations of the acoustics outside the ear, except when the hearing aid was partly removed, were found with the ITEC when a telephone set was placed by the ear. The variations of the loop response caused by changes in vent size were compared with the variations of a theoretical model of the feedback path. The theoretical model was also used to compare the feedback of different designs of the vent that gives the same acoustic impedance at low frequencies. The calculated feedback was less with the short vents (12 mm) than the long vents (24 mm). © 1999 Acoustical Society of America.
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43.66.Ts Auditory prostheses, hearing aids
43.64.Ha Acoustical properties of the outer ear; middle-ear mechanics and reflex
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