Auditory temporal summation in presbycusis and noise exposure.

Threshold-duration functions were obtained at 250, 1000, and 4999 Hz by Brief-Tone Békésy Audiometry. Results for an older group (51-57 yrs.) with no otological abnormalities showed the presence of depressed threshold-duration functions with a decreased constant of temporal summation when compared to a young normative group. The effect is frequency dependent and is most pronounced at 4000 Hz. The older group, divided into noise exposed and non-noise exposed subsamples, showed identical threshold-duration functions and resembled those for a young noise exposed group. Auditory temporal summation appears to be affected by the neuorphysiological disturbances of presbycusis and at least from 51 to 57 years is independent of noise exposure.