A comparison of recognition performances in speech-spectrum noise by listeners with normal hearing on PB-50, CID W-22, NU-6, W-1 spondaic words, and monosyllabic digits spoken by the same speaker.

BACKGROUND So that portions of the classic Miller, Heise, and Lichten (1951) study could be replicated, new recorded versions of the words and digits were made because none of the three common monosyllabic word lists (PAL PB-50, CID W-22, and NU-6) contained the 9 monosyllabic digits (1-10, excluding 7) that were used by Miller et al. It is well established that different psychometric characteristics have been observed for different lists and even for the same materials spoken by different speakers. The decision was made to record four lists of each of the three monosyllabic word sets, the monosyllabic digits not included in the three sets of word lists, and the CID W-1 spondaic words. A professional female speaker with a General American dialect recorded the materials during four recording sessions within a 2-week interval. The recording order of the 582 words was random. PURPOSE To determine-on listeners with normal hearing-the psychometric properties materials presented in speech-spectrum noise. RESEARCH DESIGN A quasi-experimental, repeated-measures design was used. STUDY SAMPLE Twenty-four young adult listeners (M = 23 years) with normal pure-tone thresholds (< or = 20-dB HL at 250 to 8000 Hz) participated. The participants were university students who were unfamiliar with the test materials. DATA COLLECTION AND ANALYSIS The 582 words were presented at four signal-to-noise ratios (SNRs; -7-, -2-, 3-, and 8-dB) in speech-spectrum noise fixed at 72-dB SPL. Although the main metric of interest was the 50% point on the function for each word established with the Spearman-Kärber equation (Finney, 1952), the percentage correct on each word at each SNR was evaluated. The psychometric characteristics of the PB-50, CID W-22, and NU-6 monosyllabic word lists were compared with one another, with the CID W-1 spondaic words, and with the 9 monosyllabic digits. RESULTS Recognition performance on the four lists within each of the three monosyllabic word materials were equivalent, +/- 0.4 dB. Likewise, word-recognition performance on the PB-50, W-22, and NU-6 word lists were equivalent, +/- 0.2 dB. The mean recognition performance at the 50% point with the 36 W-1 spondaic words was approximately 6.2 dB lower than the 50% point with the monosyllabic words. Recognition performance on the monosyllabic digits was 1-2 dB better than mean performance on the monosyllabic words. CONCLUSIONS Word-recognition performances on the three sets of materials (PB-50, CID W-22, and NU-6) were equivalent, as were the performances on the four lists that make up each of the three materials. Phonetic/phonemic balance does not appear to be an important consideration in the compilation of word-recognition lists used to evaluate the ability of listeners to understand speech. A companion paper examines the acoustic, phonetic/phonological, and lexical variables that may predict the relative ease or difficulty for which these monosyllable words were recognized in noise (McArdle and Wilson, this issue).