Sentence reception in noise from one versus two sources: Effects of aging and hearing loss

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Abstract
Sentence reception thresholds (SRTs) and babble detection thresholds (BDTs) were measured for signals presented from loudspeakers located at 0 deg and 90 deg azimuth. In addition, the S/B ratios necessary to achieve SRT in the presence of a 12-talker babble were determined under three conditions in which the speech and babble were presented from the same of spatially separated loudspeakers. In the first experiment, normal-hearing subjects were tested on two occasions. The results were highly reliable, with standard errors of the test-retest differences of less than 1dB for all conditions. In the second experiment, SRTs, BDTs, and S/B ratios were measured for three normal-hearing groups (.ltoreq. 39, 40-54, and .gtoreq. 55 years) and for a fourth group with presbycusics (.gtoreq. 55 years). Presbycusics had higher SRTs and BDTs than all other groups regardless of asge, and the oldest normals had higher thresholds than younger subjects. Presbycusics required higher S/B ratios than any of the normal groups, and the oldest normal group needed a higher S/B ratio compared to the youngest group. All groups demonstrated a significant advantage in S/B ratio when the sentences and babble sources were spatially separated compared to when they were presented from the same loudspeaker. There was no significant difference in the magnitude of advantage due to spatial separation of speech and noise between the normal groups regardless of age, but the presbycusics had significantly smaller advantages than all normals. These findings suggest that aging alone does not impair the ability to take advantage of the spatial separation of speech and noise, and that the speech reception problems of aging individuals involve various components that depend upon the nature of the listening task.