Speech intelligibility, localization, and binaural detection with monaural and binaural amplification

As part of a continuing study of monaural and binaural amplification, performance on binaural detection, speech intelligibility, and localization was measured for four listeners with bilateral, sensorineural hearing losses, and one listener with a unilateral sensorineural loss. Masking-level differences (MLDs) were measured using speech-spectrum noise maskers and octave-band speech-spectrum noise targets. Localization was measured in anechoic and reverberant environments using three-word phrases at nine locations in the horizontal plane. Intelligibility of monosyllabic words was assessed in quiet and in three signal and noise configurations (0/0, 0/+90, 0/−90) in anechoic and reverberant environments. Performance on all three tests varies among hearing-impaired listeners, even those with similar hearing losses, and is generally poorer than normal-hearing listeners. In most cases, subjects with bilateral losses have better speech intelligibility and localization and larger MLDs with binaural amplification than monaural amplification. Listening environment does not appear to affect localization or speech intelligibility in quiet, but speech intelligibility in noise is usually better in the anechoic environment. Combined data for all the subjects shows a tendency for the S/N ratios for 50% speech intelligibility and the rms localization errors to decrease as MLDs increase. [Work supported by NIH Grant No. DC00428.]