Masking-level difference for spondaic words in 2000-msec bursts of broadband noise.

One protocol developed for the Tonal and Speech Materials for Auditory Perceptual Assessment audio compact disc was the masking-level difference (MLD) for spondaic words in which the words and broadband noise were mixed and recorded at 16 selected signal-to-noise ratios. Four words were recorded at each level. Because it was impossible to monitor the word presentations at negative signal-to-noise ratios, a different paradigm was devised in which the spondaic words were embedded in 2000-msec bursts of noise. Before the materials were finalized for the compact disc, two experiments studied the perceptual characteristics of the paradigm. Experiment I was performed to determine the characteristics of the MLD for spondaic words in 2000-msec bursts of noise at 70 dB SPL. An unexpected finding was that the mean SoNo thresholds were at signal-to-noise ratios 3-4 dB lower than previously reported spondaic word thresholds in continuous broadband noise. Experiment II examined this discrepancy with the spondaic words embedded in continuous noise and in the 2000-msec noise bursts. The results confirmed the 3-4 dB difference between thresholds for the two masker conditions. Based on the pilot data, the spondaic words embedded in 2000-msec bursts of broadband noise at signal-to-noise ratios of 0 dB to -30 dB were recorded on the compact disc in the S pi No paradigm. In the compact disc trials, which involved 120 subjects with normal hearing, the MLDs for the spondaic words recorded on the compact disc were measured on 60 subjects at each of two noise levels.(ABSTRACT TRUNCATED AT 250 WORDS)