Influence of overstimulation on temporary threshold shift and the onset of aural overload.

This investigation sought to examine the sensitivity of pure tone thresholds and the onset of aural overload to the fatiguing effects of broad band noise. Noise levels ranging from 35 to 110 dB SPL were presented to 8 normal hearers. Post-exposure pure tone thresholds were determined for octave frequencies 500-4000 Hz while aural overload thresholds were obtained for the fundamental frequencies of 500 and 2000 Hz. Aural overload thresholds were found to decline following exposure levels insufficient to produce measurable TTS. This was particularly evident for low-frequency stimuli (below 2000 Hz). Results suggested that the aural overload test may be a more effective indication of cochlear damage than is the traditional temporary threshold shift procedure. These findings are discussed in terms of the "injured hair cell" hypothesis proffered by Wever & Lawrence (1955).