ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pPP2. Informational masking in the identification of simple auditory patterns.

Dept. of Commun. Disorders, Boston Univ., 635 Commonwealth Ave., Boston, MA 02215

Listeners identified six auditory patterns comprised of eight sequential tone bursts [cf. Kidd et al., 2916(A) (1994)]. Several factors affecting performance were examined including center frequency, level and the size of the frequency steps forming the patterns. In masked conditions, a multitone masker was played synchronously with each pattern element. The components of the multitone masker were chosen randomly on every burst within a presentation interval. Masker components were excluded from a region of 20% of the pattern center frequency to minimize ``energetic masking.'' The results in quiet indicated that identification performance was nearly perfect for pattern frequency steps as small as 1% and at levels as low as 20 dB SL. Considerable ``informational masking'' was produced by the random multitone masker bursts. The masked identification-level functions were shallow, rising on average about 2% per dB. Several signal and masker presentation schemes were examined that were intended to reduce the observed masking. To date, the most effective means for improving signal pattern identification has been to present the signal to one ear and identical maskers to both ears with the masker leading in time (8 ms) in the ear contralateral to the signal. [Work supported by NIH.]