Low- and high-pass filtered Northwestern University Auditory Test No. 6 for monaural and binaural evaluation

Two protocols developed for the Tonal and Speech Materials for Auditory Perceptual Assessment audio compact disc are low- and high-pass filtered versions of the Northwestern University Auditory Test No. 6 (female speaker). Two experiments were performed on subjects with normal hearing to determine the needed filter characteristics of the words. In Experiment I, word-recognition performance was determined at 70 dB SPL for four low-pass cut-offs (800 to 1700 Hz) and for four high-pass cut-offs (1700 to 3000 Hz). Based on the data from Experiment I, the low-pass (1500-Hz cut-off) and high-pass (2100-Hz cut-off) conditions were selected for inclusion on the compact disc. In Experiment II, psychometric functions were obtained in quiet for the two filter conditions with lists 3 and 4 included on the compact disc. Because the high-pass filtered words were recorded on channel 1 and concurrently the corresponding low-pass filtered words were recorded on channel 2, a binaural fusion paradigm is also available on the compact disc. For the compact disc trials, which involved 120 subjects with normal hearing, psychometric functions were generated for monaural low-pass, monaural high-pass, and binaural spectral fusion (low- and high-pass) conditions, with each of the subjects providing data at one of six levels for each of three conditions.