Marjorie R. Leek
Army Audiol. and Speech Ctr., Walter Reed Army Med. Ctr., Washington, DC 20307-5001
Upward spread of masking (USM), the masking of an acoustic signal by energy at lower frequencies, tends to increase with presentation level and is more pronounced in listeners with sensorineural hearing impairment (HI listeners) than in normal-hearing (NH) listeners. At high presentation levels, HI listeners may experience a decrease in the cues available from higher frequency regions due to masking produced by high-amplitude first formant (F1) resonances. In the present study HI and NH listeners labeled synthetic consonant--vowel stimuli at moderate and high presentation levels. F1 regions were attenuated by 0, 6, 12, or 18 dB to test whether F1 attenuation might reduce USM, making cues present at higher frequencies more available. Performance was tested in quiet and in broadband noise sufficient to mask initial consonantal bursts. For both groups of listeners, noise reduced labeling accuracy. For normal-hearing listeners, performance was not affected by presentation level or F1 attenuation. While some HI listeners showed clear improvements in labeling with F1 attenuation and/or increases in presentation level, the pattern did not hold across the entire group. The results will be discussed in light of the severity and configuration of the individual hearing losses.