The role of sequential stream segregation and frequency selectivity in the perception of simultaneous sentences by listeners with sensorineural hearing loss.

The purpose of this study was to determine the role of frequency selectivity and sequential stream segregation in the perception of simultaneous sentences by listeners with sensorineural hearing loss. Simultaneous sentence perception was tested in listeners with normal hearing and with sensorineural hearing loss using sentence pairs consisting of one sentence spoken by a male talker and one sentence spoken by a female talker. Listeners were asked to repeat both sentences and were scored on the number of words repeated correctly in each sentence. Separate scores were obtained for the first and second sentences repeated. Frequency selectivity was assessed using a notched-noise method in which thresholds for a 1,000 Hz pure-tone signal were measured in noise with spectral notch bandwidths of 0, 300, and 600 Hz. Sequential stream segregation was measured using tone sequences consisting of a fixed frequency (A) and a varying frequency tone (B). Tone sequences were presented in an ABA_ABA_... pattern starting at a frequency (B) either below or above the frequency of the fixed 1,000 Hz tone (A). Initially, the frequency difference was large and was gradually decreased until listeners indicated that they could no longer perceptually separate the two tones (fusion threshold). Scores for the first sentence repeated decreased significantly with increasing age. There was a strong relationship between fusion threshold and simultaneous sentence perception, which remained even after partialling out the effects of age. Smaller frequency differences at fusion thresholds were associated with higher sentence scores. There was no relationship between frequency selectivity and simultaneous sentence perception. Results suggest that the abilities to perceptually separate pitch patterns and separate sentences spoken simultaneously by different talkers are mediated by the same underlying perceptual and/or cognitive factors.