Review of four new indices of susceptibility to noise-induced hearing loss.

The potential use of four new measures of susceptibility to acoustic trauma has been discussed. Each has the advantage, unlike TTS methodology, of not requiring a prior exposure stimulus. The use of an exposure sound has proven to be the major drawback to verification of Temkin's original hypothesis. A disadvantage inherent to the speech discrimination procedures involves the use of difficult-to-standardize speech materials and techniques. Consequently, one of the first three techniques, aural overload, threshold of octave masking, and brief-tone audiometry, is more desirable with aural overload having the most data to substantiate its use as a predictor of vulnerability to ear damage from acoustic overstimulation. None of these tests, on the other hand, has been correlated to permanent threshold shift (PTS). This necessitates the use of experimental animals or the long-term monitoring of the hearing sensitivity of industrial workers. Such data should prove invaluable in the search for an effective predictor of eventual noise-induced hearing loss.