Speech recognition threshold in slightly and fully modulated noise for hearing-impaired subjects.

A previously developed speech test with sentences in noise was modified in an attempt to increase its efficiency. Thus the original, slightly modulated (SM) noise was changed to be fully modulated (FUM), and the speech-to-noise ratio of each word was controlled to make all the words equally difficult. The new and the old version were compared in 41 hearing-impaired subjects. The learning effect was similar for both noises, but the variability was higher for the FUM noise. However, the efficiency of the speech test was slightly better for the FUM noise. Speech recognition in both types of noise was correlated with pure-tone thresholds at high frequencies, i.e. 2000 Hz and above, but not to tone thresholds at lower frequencies. Results in FUM noise and in SM noise were highly correlated, with a correlation coefficient of 0.86.