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May 1984

Volume 75, Issue S1, pp. S1-S93

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back to top Session DD. Psychological Acoustics VI: Masking
Contributed Papers
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Transition from simultaneous to forward masking (A)

Daniel L. Weber

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S56-S56 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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A stimulus condition in which the signal presentation partially overlaps the end of the masker presentation is intermediate between a simultaneous masking condition (complete overlap) and a forward masking condition (no overlap). The question is, “What process underlies signal detection in this condition?” To answer this question, this experiment examines the masked threshold for a 20‐ms, 1‐kHz sinusoidal signal (20‐ms cosine‐squared ramps with no steady state) as a function of the temporal position of the signal with respect to a 400‐ms, 1‐kHz, 70‐dB SPL sinusoidal masker (quadrature phase, 0‐ms ramps). These thresholds are compared to those obtained for the portion of each signal which occurred after the masker; these “partial” signals had 1‐ms onset ramps which rose during the final 1 ms of the masker; the beginning portion of the 20‐ms signal (the portion which overlapped the masker) was eliminated. When the threshold for the whole signal equals the threshold for the partial signal (which necessarily is determined by the process of forward masking), one may easily argue that the “simultaneous” portion of the signal did not measurably influence signal detection. The data show that signal thresholds in transition conditions are determined by forward masking for stimulus overlaps as great as 90%. [Research supported by NSF and NIH.]
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Masking period patterns: presentation of a model consistent with an enlarged set of experimental results (A)

Jean‐Luc Schwartz and Pierre Escudier

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S56-S56 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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Masking period patterns (MPP) have been proposed by Zwieker as psychoaoustic equivalent of period histograms (PSTH) measured in auditory neurons. A large set of results have been obtained and represented on a model for predicting MPP [E. Zwicker, Biol. Cybern. 23, 49–60 (1976)]. We have already used this technique for studying PSTH when the basilar membrane is stimulated by trapezoidal patterns of excitation [P. Escudier et al., J. Acoust. Soc. Am. Suppl. 1 67, S102 (1980)]. Our results cannot be completely interpreted on the basis of Zwicker's model. We present a new model, using a peripheral auditory system simulation previously elaborated in our group [J. M. Dolmazon et al., Speech Commun. 1, 52–73 (1982)] and some simple additional hypotheses. This model is shown to be able to predict the whole set of available MPP results.
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Forward masking by two sequential sinusoidal maskers (A)

Donna L. Neff

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S56-S56 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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Two temporally distinct maskers of 300 and 30 ms were used to forward mask a 10‐ms signal. The signal was a 1000‐Hz sinusoid. The maskers were either 900‐ or 1000‐Hz sinusoids and all four combinations of the masker frequencies were tested. From growth‐of masking functions for individual maskers, levels were chosen to produce 5, 10, or 15 dB of masking for the first masker and 5, 10, 15, or 20 dB of masking for the second masker. When the two maskers were combined, the amount of additional masking, relative to that produced by the more effective masker, ranged from 0–24 dB across listeners and conditions. The smallest amount of additional masking was observed when both maskers were 1000 Hz. The remaining frequency combinations produced roughly similar amounts of additional masking. The results will be discussed in terms of models of additional masking. [Work supported by NIH.]
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Presentation‐order effects in the discrimination of rapidly presented short intervals (A)

Gregory J. Fleet and Brian R. Shelton

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S56-S57 (1984); (2 pages)

Online Publication Date: 12 Aug 2005

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We previously reported a forward masking effect in a duration discrimination task [G. J. Fleet and B. R. Shelton, J. Acoust. Soc. Am. Suppl. 1 74, S10 (1983)], suggesting that the restriction of performance in the discrimination of rapidly presented brief durations was peripheral. This would predict a presentation‐order effect, where a long‐short discrimination would be easier than short‐long. Two experiments examined this idea. The first study was two‐interval forced‐choice paradigm, with the thresholds for the long‐short and short‐long presentations adapted separately. A second experiment examined these same discriminations in a same‐different paradigm. Signals were 80‐dB SPL noise bursts fast gated in a continuous 60‐dB noise background. Base durations of 25, 50, 100, and 200 ms were used, with ISI values of 25, 50, 100, 200, 400, 800, and 1600 ms. Counter to expectations, thresholds were much lower for the short‐long presentations. These data are discussed in terms of their relation to the proposed peripheral limitation thesis, as well as the arguments that this presentation‐order effect is the result of perceptual or assimilation effects. [Work supported by NSERC.]
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Duration and rise‐decay time in the masking‐level difference obtained in pulsed masker conditions (A)

William A. Yost and R. Dye, Jr.

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S57-S57 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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The MLD (masking‐level difference) is small when the signal and masker are pulsed together. The addition of a forward “masker fringe” to the pulsed signal‐puls‐masker can increase the pulsed MLD to that obtained when the masker is on continuously. The masker fringe must be at least 500 ms in order for the MLD to be as large as that obtained in the continuous masker condition. A parametric study of masker‐plus‐signal duration in the pulsed conditions and signal rise‐decay time in the continuous masker conditions were investigated. Masked thresholds in the NoSo and NoSπ conditions were obtained at 500 Hz from two‐point psychometric functions determined in a single‐interval procedure. The study was designed to test predictions of the equalization‐cancellation model for the MLD and to test the assumption that the small pulsed MLD is due to a lack of change in interaural parameters at signal onset. [Work supported by NSF.]
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Effects of masker level on binaural masking patterns (A)

Janet Koehnke and Marion F. Cohen

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S57-S57 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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This study investigated the effects of masker level on the shape of masking patterns for binaural detection. Specifically, detection thresholds of a 700‐Hz sinusoidal signal were measured as a function of the center frequency of a narrow‐band masking noise. Thresholds for the 350‐ms tone were measured twice at four masker levels, once with the signal presented diotically and once with the signal interaurally phase reversed. The masker was a continuous, diotic 80‐Hz‐wide noise that varied in frequency over a range of four critical bands above and below the signal frequency. Results show that the shape of the masking pattern varies as a function of masker level: with low‐level maskers there is a downward spread of masking; with a moderate‐level masker, masking is symmetrical; and with a high‐level masker there is an upward spread of masking. This dependence is comparable to that observed in monaural masking patterns [E. Zwicker, Audiology 19, 330–334 (1980); E. Zwicker and A. Jaroszewski, J. Acoust. Soc. Am. 71, 1508–1512 (1982)]; this similarity suggests that frequency analysis in the monaural and binaural auditory systems is similar. [Work supported by NIH grant ROI NS16802 and 2T32 NS07099‐06.]
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Effects of noise and cubic‐difference‐tone behavior (A)

Susan J. Norton, Theresa Langer, and Walt Jesteadt

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S57-S57 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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It has been suggested that external noise maskers, like sensorineural hearing loss, have a linearizing effect on cochlear function and that external noise maskers can be used to simulate sensorineural hearing loss. To test these hypotheses, cubic‐difference‐tone (CDT) behavior was measured in normal hearing listeners using a forward‐masking paradigm for sinusoidal primaries presented in quiet and in the presence of low‐pass, high‐pass, and broadband noise. The noise was presented only during the primaries and could be considered as an additional forward masker. None of the noises used affected CDT behavior in a way that would support the hypothesis that noise has a linearizing effect on cochlear function. The range over which cubic difference tones could be measured was shifted by the amount that the thresholds for the primaries were shifted, but otherwise CDT behavior was similar to that observed in quiet. In contrast with results reported for persons with high‐frequency sensorineural hearing loss, high‐pass noise above the primaries had no effect on CDT behavior. Low‐pass noise also had no effect on CDT behavior. Broadband noise added with the CDT much like external sinusoids and noise add. [Work supported by NIH.]
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The prediction of masking in helicopters (A)

R. D. Patterson, M. Lower, P. Wheeler, and G. Rood

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S57-S57 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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The spectrum of the noise in helicopters is complicated because the rotor and blades produce intense low‐frequency noise components, and the gears and transmission produce narrow‐band peaks in the mid‐frequency range. Thus the helicopter provides an excellent proving ground for theoretical models of auditory masking. The rounded exponential model of masking [Patterson et al., J. Acoust. Soc. Am. 57, 1788–1803 (1982)] has been extended to predict threshold at low frequencies and high levels by incorporating the results of recent laboratory studies. Two experiments were then performed to test the model's ability to predict masked audiograms gathered in the presence of helicopter noise. In one experiment the masker was presented via headphones in sound attenuating chambers to 12 listeners, in the other the masker was presented via loudspeakers in a Lynx helicopter simulator to six listeners. The results show that a very simple auditory filter, Roex (p), and mild asymmetry (upper side sharper) can predict the data well.
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