Intraspeech spread of masking in normal-hearing and hearing-impaired listeners

Hearing-impaired and normal-hearing listeners labeled synthetic consonant-vowel stimuli (/ba/, /do/, /ga/, /be/, /de/, /ge/) presented at moderate and high signal levels. First formant (F1) regions were synthesized at normal and at attenuated levels to test whether F1 attenuation might reduce upward spread of masking, making information contained in higher formant regions more available. Performance was tested in quiet and in broadband noise sufficient to mask initial release bursts. Although complete removal of F1 consistently reduced performance, F1 attenuation of up to 18 dB led to increased labeling accuracy, particularly in the /a/ vowel context. Benefit associated with F1 attenuation was more consistently seen for hearing-impaired than for normal-hearing listeners and, in particular, for listeners with steep increases in audiometric thresholds between the first and second formant regions of the test stimuli. The availability of initial bursts as a source of place cues during testing in quiet did not reduce the benefit associated with F1 attenuation.