Amplitude-modulation detection at low- and high-audio frequencies

Estimates of temporal acuity under comparable conditions at low- and high-audio frequencies are rare. The present study used the amplitude-modulation detection paradigm to estimate temporal acuity over a range of audio frequencies from 800 to 12,800 Hz. Amplitude-modulation detection was measured as a function of modulation frequency for bandlimited noise carriers, and the resulting temporal modulation-transfer functions were used to characterize temporal acuity. The most important result from the two experiments reported is that systematic manipulations of carrier upper-cutoff frequency produced estimates of temporal acuity that did not vary from 800 to 12,800 Hz. When the modulated noise bands were filtered after modulation to control for potential spectral cues, the low-pass cutoff of the modulation-transfer function varied with the carrier bandwidth. However, when the standard stimulus was a quasifrequency-modulated (QFM) noise and the signal was an unfiltered, amplitude-modulated noise, the low-pass cutoff of the modulation-transfer function was independent of carrier bandwidth. These results are consistent with a growing body of evidence demonstrating that auditory temporal acuity is constant throughout most of the audible frequency range.