Masking produced by sinusoids of slowly changing frequency

Abstract

A fixed amplitude sinusoid that was frequency modulated by a sawtooth or triangle wave was used to mask a 20-msec pure-tone signal. The linear portions of the modulating waveforms were 150 msec in duration and swept the masker frequency between 1.5 and 0.75 kHz. A frequency contour of the masking was obtained when the temporal position of the signal was fixed relative to the sawtooth or triangle and the signal frequency was varied. A temporal contour of the masking was measured when the signal frequency was fixed and the temporal position of the signal was varied. Temporal and frequency selectivity indicated by differences of 30-40 dB of masking were observed in both kinds of contours. A linear model consisting of a bandpass filter followed by a power integrator provided a fair approximation to principal features of the masking contours when the bandwidth of the filter was 100-200 Hz and the time constant of the integrator was 10 msec. Similar resonant systems are found in spectrum channel vocoders and in instruments that produce speech spectrograms. The model tends to underestimate the masking at the higher frequencies and does not exhibit the type of deep, narrow-band notches that are found in frequency contours of the masking.

The role of the bandwidth-duration product WT in the detectability of diotic signals

“…The correlation analysis (Chapter 5) results showed higher correlations between human ratings and simulated observers, when a true integrator, or a leaky integrator with a very long time constant, was used. This is consistent with the findings of Makita and Miyatani (1950) and Henning and Psotka (1969), but not consistent with studies supporting leaky integration with a short time constant (Jeffress, 1967(Jeffress, , 1968Robinson & Pollack, 1973;Robinson, 1974;Ronken, 1973).…”

“…Studies that have found evidence that the time constant of the temporal integrator was short include Robinson and Pollack (1973), Robinson (1974), andRonken (1973). Studies that have found long duration (greater than 200 ms) time constants include Makita and Miyatani (1950) and Henning and Psotka (1969).…”

Masking patterns for continuous and gated sinusoids

“…In order to generate quantitative predictions, two free parameters of the model, the time constant of the integrator and the amplitude response of the auditory filter, had to be estimated from steadystate masking data. The present analysis employed a 16-msec time constant, which is in accord with a number of other psycho-acoustic results (Ronken, 1973). The off-band attenuation rate of the auditory filter was estimated directly from the masking pattern obtained in the continuous masker condition.…”

The temporal processes of auditory excitation produced by frequency modulated tones.

“…3) Some authors reported the masking time pattern using periodically -frequency-modulated tones as maskers, where the test tone bursts were short enough to enable their insertion at distinct temporal locations within the masker's period. [4][5][6] This type of masking is called the masking period pattern. However, there are few studies on the masking for tones as maskers with transient frequency change.…”