Dynamic range and asymmetry of the auditory filter

Abstract

The shape and asymmetry of the auditory filter, over a wider dynamic range than has been measured previously, was measured. Thresholds were measured for 2-kHz sinusoidal signals in the presence of 2 800-Hz-wide noise bands, 1 above and 1 below the signal frequency. The spectrum level of the noise was 45 dB (re: 20 .mu.Pa [Pascall]), and the noise bands were placed both symmetrically and asymmetrically about the signal frequency. The deviation of the signal frequency from the nearer edge of each noise band varied from 0-0.8 times the signal frequency. Each ear of 6 subjects was tested, and the subjects'' ages ranged from 22-74 yr. The auditory filters derived from the data were somewhat asymmetric, with steeper slopes on the high-frequency side; the degree of asymmetry varied across subjects. The asymmetry could be characterized as a uniform stretching of the (linear) frequency scale on 1 side of the filter. The dynamic range of the auditory filter exceeded 60 dB in the younger listeners, but the dynamic range and sharpness of the filter tended to decrease with increasing age.