Clinical measures of static and dynamic spectral-pattern discrimination in relationship to speech perception

Two experiments evaluated discrimination ability for both static and dynamic spectral patterns. The static conditions measured the ability to detect a change in the phase of a low-rate sinusoidal spectral ripple of wideband noise. The dynamic condition determined the signal-to-noise ratio (SNR) needed to discriminate 1-kHz pure tones frequency modulated by different 5-Hz lowpass noise samples drawn from the same underlying noise distribution so that discrimination was based on the temporal pattern of fluctuation. Both procedures used a modified descending method of limits with test stimuli recorded on a CD for clinic use. Results from the first experiment showed a significant relationship of both metrics to masked speech intelligibility. Using only the static procedure, the second experiment evaluated the role of fine-structure information in the perception of masked speech through vocoding of psychoacoustic and speech stimuli. In this case, results showed significant relationship only when the psychoacoustic and speech stimuli were either both vocoded or both unprocessed, consistent with involvement of stimulus fine structure in speech perception at low SNRs. Overall, results from both experiments support clinical utility of the procedures in the context of speech processing ability.