Normal hearing thresholds for clicks.

This paper evaluates the normal hearing thresholds for clicks and assesses the effects on these thresholds of varying the duration of the listening period and the presentation rate, polarity, and symmetry of the clicks. There were no significant changes in thresholds as the listening period decreased from 2s to 300 mg. There was, however, a 2.5 dB increase in threshold at the listening period decreased from 300 to 100 ms. Increase stimulus presentation rate from 5 to 80/s decreased threshold 4.5 dB per tenfold change in rate. There were no significant differences in threshold between rarefaction and condensation clicks. The average threshold obtained from 40 normal young adults using 100-microseconds square-wave clicks presented through a TDH-49 earphone at 10/s was 36.4-dB peak SPL or 29.9 peak equivalent SPL. Neither peak SPL nor peak equivalent SPL measurements gave consistent thresholds for clicks with different degrees of symmetry. A root-mean-square measure of the pressure over the initial millisecond-SPL(1 ms)-gave a threshold of 25.6 dB. This SPL(1ms) measure of threshold proved to be far more consistent for clicks with different degrees of symmetry than either the peak SPL or the peak equivalent SPL measures.