Psychophysical tuning curves independent of signal level

Abstract

Psychophysical tuning curves were obtained for three subjects in a forward masking paradigm, with signal levels of 21, 30, and 50 dB SPL at 1000 Hz and 30, 40, and 50 dB SPL with a 3000-Hz signal. All tuning curves were measured in quiet and with a background noise adjusted to produce a constant signal-to-noise ratio of E/N0 = 16 dB. The results indicated that the tuning curves obtained in quite change shape with increasing signal level, whereas the shapes of tuning curves measured in noise are the same at all signal levels. A control condition demonstrates that only signal energy in a narrow band near the signal frequency is useful in detecting the signal. This control along with the invariance of tuning curve shape with signal level support the interpretation that the broadening of tuning curves with increased signal level, observed when the signals are presented in quiet, is caused by the presence of off-frequency components.

Upward shifts in the masking pattern with increasing masker intensity

“…In some of these experiments, performance has been measured at a number ofmasker and/or signal frequencies, and more rarely, at a number of intensities as well. A frequency shift in the point of maximal masking has sometimes been found {e.g., Moore, 1978Widin and Viemeister, 1979a;Fastl, 1974;Kidd and Feth, 1981}, and has sometimes not been found {Vogten, 1978b; Green et al, 1981;Houtgast, 1973, Fig. 3;Norton and Wier, 1981;Ehmer and Ehmer, 19691, but even when found, it has typically been a much smaller shift than was reported by Munson and Gardner {1950} and Zwislocki and Pirodda {1952}.…”

Additivity of simultaneous masking

“…Studies indicate that as the level of a sinusoidal signal is increased the internal representation of the signal occupies a greater number of off-frequency channels thereby increasing the potential off-frequency listening advantage (Green et al, 1981;Verschuure, 1978;Zwicker, 1974). These data imply that the off-frequency advantage is negligible at low-signal levels (10 dB SL) but becomes quite large at higher signal levels (40-50 dB SL).…”

“…As an added control for the effects of off-frequency listening, masking functions were also obtained for the 1.9 and 2.1-kHz narrow-band noise masketa individually and in combination in the presence of a continuous low-level broadband background noise. The inclusion of a low-level background noise is a common procedure for restricting off-frequency listening (Green et al, 1981 ).…”

Level dependence of auditory filters in nonsimultaneous masking as a function of frequency

“…In any case, to the extent that nonsimultaneous masking better reflects cochlear tuning, as measured physiologically, it seems that pronounced differences occur between 1 and 6 kHz, which are not captured by current phenomenological models of human auditory filtering (e.g., Glasberg and Moore, 2000;Meddis et al, 2001). One study measured psychophysical tuning curves as a function of level at both 1 and 3 kHz (Green et al, 1981). They found level independence over a 20-dB range of signal levels at both frequencies.…”