Audibility of Periodic Pulses and a Model for the Threshold Available to Purchase

Thresholds of audibility are determined by the Békésy technique for four periodic trains of rectangular pulses. The pulses of a given train are uniform in amplitude and duration, and the trains differ in their periodic patterns of pulse polarity. The parameters considered are pulse rate, pulse duration, and polarity pattern. The stimuli are presented binaurally in quiet over headphones. Data for four subjects are reported. The results show the threshold amplitudes to be little dependent upon polarity pattern. For pulse rates less than about 100 pps the thresholds are also little dependent upon pulse rate. They approach constant values determined by pulse duration. Above 100 pps the thresholds diminish with increasing pulse rate. The experimental technique also provides an estimate of the intensity limen at threshold. An analytical specification of the stimulus is derived which provides an objective correlate of the threshold percept. An electrical circuit model of the threshold is developed which takes account of middle‐ear and basilar membrane transmission. The threshold model reflects a constancy of percept over a pulse‐rate range of 10 octaves and a pulse‐duration range of ten to one. Its application to the metering of subjective loudness is suggested.