Is higher acoustic energy at faster rates necessary for the click-rate-induced improvement in acoustic reflex thresholds?

Ipsilateral click thresholds can improve by approximately 21 dB, with an increase in the click repetition rates from 50/s to 300/s [Rawool, Scand. Audiol. 24, 199–205 (1995)]. When click‐trains are presented over the same duration (e.g., 1.5 s), the number of clicks presented at the lower rates is less than the number of clicks presented at the higher repetition rates. Thus there is more total energy for the higher repetition rates. Therefore, it has been proposed that an important factor contributing to the threshold advantage for higher repetition rates could be the number of clicks. This investigation was designed to evaluate acoustic reflex thresholds at various repetition rates using a constant number of clicks (constant acoustic energy). Ipsilateral acoustic reflex thresholds were obtained from 19 normal female left ears by presenting 300 clicks at the repetition rates of 50, 100, 150, 200, and 300/s. The frequency of the probe tone was 226 Hz (85 dB SPL). The results showed a significant improvement (mean = 17 dB) in acoustic reflex thresholds with the increase in repetition rates. Thus the improvement in acoustic reflex thresholds with the increase in the repetition rate can occur as a function of the rate itself, even if a constant number of clicks are presented at each rate.