Forward masking as a function of frequency, masker level, and signal delay

1982 ◽  
Vol 71 (4) ◽  
pp. 950-962 ◽  
Author(s):  
Walt Jesteadt ◽  
Sid P. Bacon ◽  
James R. Lehman
Keyword(s):  
Forward Masking ◽  
Signal Delay ◽  
Masker Level

Forward masking of auditory nerve fiber responses

1979 ◽  
Vol 42 (4) ◽  
pp. 1083-1107 ◽  
Author(s):  
D. M. Harris ◽  
P. Dallos
Keyword(s):  
Time Constant ◽  
Auditory Nerve ◽  
Time Course ◽  
Forward Masking ◽  
Response Magnitude ◽  
Masking Effect ◽  
Masker Level ◽  
Frequency Threshold ◽  
Masking Stimulus ◽  
Probe Response

1. Responses of single fibers were obtained from the auditory nerve of chinchillas. Tone-burst stimuli consisted of a masking stimulus followed by a probe stimulus. Forward masking of a fiber's response is defined as a reduction in the magnitude of the probe-evoked response caused by the addition of the masking stimulus. 2. The recovery of probe response magnitude as a function of the time interval between masker offset and probe onset (delta T) follows an exponential time course. A relationship between the time course or magnitude of poststimulus recovery and the characteristic frequency (CF) of a fiber was not detected. 3. The iso-forward masking contour near the threshold of the masking effect across masker frequencies approximates a fiber's frequency threshold curve (FTC). In other words, forward masking tuning curves are essentially the same as frequency threshold curves. 4. The frequency dependence of forward masking is compared to that of two-tone suppression. Tonal stimuli outside the boundaries of a fiber's FTC that produce two-tone suppression are ineffective forward maskers. Certain frequency/intensity combinations within the FTC may produce both suppression and forward masking and tones within the remaining area of the FTC produce no suppression but are effective forward maskers. 5. Both the time course and the magnitude of the forward masking effect are dependent on the discharge rate evoked by the masker regardless of the masker's absolute level or spectral content. An increase in masker-evoked excitation causes an increase in time constant and a greater reduction in probe response magnitude, rd. The function relating rd to masker level parallels the firing rate/masker level function up to 40 dB above response threshold. 6. A decrease in masker duration from 100 ms leads to a decrease in both rd and the time constant of recovery. There is no significant difference between the 100 and 200 ms duration conditions. 7. Forward masking in single fibers is related to the period of poststimulus recovery of spontaneous activity, a component of a fiber's response pattern to the masker, and this component is tentatively identified as a period of recovery from short-term adaptation.

Forward Masking of Dynamic Acoustic Intensity: Effects of Intensity Region and End-Level

Perception ◽  
10.1068/p7128 ◽  
2012 ◽  
Vol 41 (5) ◽  
pp. 594-605 ◽  
Author(s):  
Kirk N Olsen ◽  
Catherine J Stevens
Keyword(s):  
Pure Tone ◽  
Stimulus Presentation ◽  
Forward Masking ◽  
Intensity Change ◽  
Minimal Effect ◽  
Signal Delay ◽  
Acoustic Intensity ◽  
The Difference ◽  
Response Biases ◽  
Intensity Region

Overestimation of loudness change typically occurs in response to up-ramp auditory stimuli (increasing intensity) relative to down-ramps (decreasing intensity) matched on frequency, duration, and end-level. In the experiment reported, forward masking is used to investigate a sensory component of up-ramp overestimation: persistence of excitation after stimulus presentation. White-noise and synthetic vowel 3.6 s up-ramp and down-ramp maskers were presented over two regions of intensity change (40–60 dB SPL, 60–80 dB SPL). Three participants detected 10 ms 1.5 kHz pure tone signals presented at masker-offset to signal-offset delays of 10, 20, 30, 50, 90, 170 ms. Masking magnitude was significantly greater in response to up-ramps compared with down-ramps for masker-signal delays up to and including 50 ms. When controlling for an end-level recency bias (40–60 dB SPL up-ramp vs 80–60 dB SPL down-ramp), the difference in masking magnitude between up-ramps and down-ramps was not significant at each masker–signal delay. Greater sensory persistence in response to up-ramps is argued to have minimal effect on perceptual overestimation of loudness change when response biases are controlled. An explanation based on sensory adaptation is discussed.

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