Psychophysical tuning curves for frequencies below 100 Hz

Abstract

Psychophysical tuning curves (PTCs) were measured for sinusoidal signals with frequency f(s) = 31.5, 40, 50, 63, and 80 Hz, using sinusoidal and narrowband-noise maskers. For the former, conditions were included where a pair of beating tones was added to reduce the use of cues related to beats. Estimates of each subject's middle-ear transfer function (METF) were obtained from equal-loudness contours measured from 20 to 160 Hz. With decreasing f(s), the PTCs became progressively broadened and markedly asymmetrical, with shallow upper skirts and steep lower skirts. For the sinusoidal maskers, the tips were more irregular than for narrowband-noise maskers or when beating tones were added. For f(s) = 31.5 and 40 Hz, the tips of the PTCs always fell above f(s). Allowing for the METF so as to infer underlying filter shapes resulted in flatter lower skirts, especially below 40 Hz, and reduced the frequency at the tips for f(s) between 31.5 and 50 Hz; however, the tips did not fall below 40 to 50 Hz. The bandwidths of the PTCs increased with decreasing f(s) below 80 Hz. However, bandwidths remained roughly constant if the METF was included as part of auditory filtering for frequencies below 40 Hz.

Frequency selectivity for frequencies below 100 Hz: Comparisons with mid-frequencies

“…The reversal appears to be a consequence of the highpass nature of the METF. It is also consistent with the trends we observed in the shapes of psychophysical tuning curves determined for several values of f s in the range below 100 Hz (Jurado et al, 2010a).…”

“…Here, we chose to use a fixed masker level. In other studies, we have gathered data using a fixed signal level (Jurado et al, 2010a).…”

Contributions of von Békésy to psychoacoustics

“…However, his physiological measurements led him to conclude that "the distribution of excitation in the human cochlea does not change with frequency for frequencies below 50 cps" (von Békésy, 1963a, p. 589), so he argued that for frequencies below 50 Hz a change in frequency is detected as a change in time pattern (note, however, that he was not entirely consistent about this, as Figure 22 in the same paper shows the place of maximum excitation moving further from the stapes as the frequency is decreased from 50 to 25 Hz). His argument that the "end of the cochlea" corresponds to a frequency of 50 Hz is consistent with recent measurements of psychophysical tuning curves (PTCs) for very low signal frequencies (Jurado et al, 2011). When the signal frequency is below 50 Hz, the tip of the PTC is shifted upwards; a masker centered above the signal frequency is more effective than a masker centered at the signal frequency.…”

A new method of calculating auditory excitation patterns and loudness for steady sounds

“…Signals with extremely low and high frequencies are probably detected using the outputs of filters with CFs above or below those frequencies, respectively (Moore et al, 1997). Here we assume that the CF of the highest auditory filter is 17000 Hz, based on the work of Yasin and Plack (2005) and that the CF of the lowest auditory filter is 40 Hz, based on the work of Jurado et al (2011). This corresponds to a range of Cams from 1.5 to 40.2.…”