Effects of attenuation step on descending Békésy threshold.

Abstract

For fixed suprathreshold starting intensities, Békésy thresholds were compared for interrupted tones, tones with 2.5-dB attenuation steps, and continuous tones with 0.25-dB steps in normal ears and those with cochlear lesions. Thresholds for interrupted tones were best, those for continuous tones were the worst, and those with an attenuation step of 2.5 dB were intermediate in both normal and pathological ears. The threshold difference between interrupted tones and tones with 2.5-dB steps are about two-fifths the magnitude of difference in threshold between interrupted tones and tones with 0.25-dB steps. In pathological ears, as the differences in threshold between interrupted tones and both stepped tones increased, the amount of separation between interrupted and continuous tone fixed-frequency Békésy trackings and tone decay also increased. As the differences in threshold between interrupted tones and 2.5-dB step continuous tones increased by 1 dB, threshold differences between interrupted tones and 0.25-dB step continuous tones increased by 2.3 dB in both normal ears and those with cochlear lesions. With high suprathreshold starting intensities, threshold differences for interrupted tones and continuous tones attenuated in discrete steps are probably due to normal and abnormal adaptation.