Dept. of Commun. Disord., Penn State Univ., 5 Moore Bldg., University Park, PA 16802
U.S. Army Res. Lab., Aberdeen Proving Ground, MD 21005-5425
Detection thresholds were measured for a spectrally complex target signal presented in either localized or nonlocalized speech-spectrum noise (65 dBA). Thresholds were obtained for 50 normal hearing subjects, in 40 different combinations of azimuth of the target and noise sources. In general, the results showed that the detectability of the target signal in localized noise was better than in nonlocalized noise. In the conditions where the target signal was presented in localized noise, the findings revealed that (a) poorest thresholds occurred when the target and noise were coincident; (b) thresholds improve as the amount of spatial separation between the target and noise source increases; and (c) best performance occurred when either the target or noise source was off of the median plane and at least a 45(degrees) azimuth separation existed between the sources. Improvements in detection thresholds amounted to as much as 15--18 dB, depending on the condition.