High-frequency Bekesy audiometry: VI. Pulsed vs. continuous signals.

Abstract

Carefully screened normal-hearing young adults (5M, 25 F) performed a fixed-frequency version of high-frequency Bekesy audiometry (HFBA) with pure tones ranging from 2-16 kc/s, using the SHF E-800 unit (Gauz and Smith, J. Aud. Res., 1985, 25, 101-122). Pulsed (P) and Continuous (C) traces were recorded for 1 and 2 min, respectively. Data were described in types of response, amount of threshold decrement of the C trace re P traces, and rate of threshold decrement. P traces showed stability, while the majority (about 70-95%) of C traces overlapped P traces for 2-12 kc/s (our Type I). Some C traces (about 3-25% indicated adaptation followed by stabilization (Type II), while others (about 3-20% showed adaptation without stabilization (Type II/III), without regard for frequency. Rapid adaptation to the limits of the audiometer (Type III) was infrequently encountered below 14 kc/s, but showed an accelerated increase from 14-16 kc/s. During Min 2, a slight decrease in Type I responses and a corresponding increase in Type II responses were obtained. The rate of adaptation (in db/sec) increased with frequency and decreased with duration. This slope was relatively slight at 2-8 kc/s, increased at 10-12 kc/s, and increased notably at higher frequencies. Total amount of adaptation in db (P-C) increased with frequency, although mean values were rather small, most less than 5 db and none exceeding 10 db by the end of Min 2. Excluding Type III responses, no C-mode adaptation exceeded 24 db for any individual. The potential utility of HFBA and implications for future research were discussed.