ABSTRACT
BACKGROUND: Speech recognition in noise (SRN) evaluations reveal information about listening ability that is unavailable from pure-tone thresholds. Unfortunately, SRN evaluations are not commonly used in the clinic. A lack of standardization may be an explanation for the lack of widespread acceptance of SRN testing. Arguments have been made for the utilization of steady-state speech-shaped noise vs. multi-talker babble. Previous investigations into the effect of masker type have used a monaural presentation of the stimuli. However, results of monaural SRN tests cannot be generalized to binaural listening conditions. PURPOSE: The purpose of this study was to investigate the effect of masker type on SRN thresholds under binaural listening conditions. RESEARCH DESIGN: The Hearing in Noise Test (HINT) protocol was selected in order to measure SRN thresholds in steady-state speech-shaped noise (HINT noise) and four-talker babble with and without the spatial separation of the target speech and masker stimuli. STUDY SAMPLE: Fifty native speakers of English with normal pure-tone thresholds (≤ 25 dB HL, 250-4000 Hz) participated in the study. The mean age was 20.5 years (SD 1.01). DATA COLLECTION AND ANALYSIS: All participants were tested using the standard protocol for the HINT in a simulated soundfield environment under TDH-50P headphones. Thresholds were measured for the Noise Front, Noise Left, and Noise Right listening conditions with HINT noise and four-talker babble. The HINT composite score was determined for each noise condition. The spatial advantage was calculated from the HINT thresholds. Pure-tone threshold data were collected using the modified Hughson-Westlake procedure. Statistical analyses include descriptive statistics, effect size, correlations, and repeated measures ANOVA followed by matched-pairs t-tests. RESULTS: Repeated measures ANOVA was conducted to investigate the effects of masker type and noise location on HINT thresholds. Both main effects and their interaction were statistically significant (p < 0.01). No significant differences were found between masker conditions for the Noise Front thresholds. However, for the Noise Side conditions the four-talker babble thresholds were significantly better than the HINT noise thresholds. Overall, greater spatial advantage was found for the four-talker babble as opposed to the HINT noise conditions (p < 0.01). Pearson correlation analysis revealed no significant relationships between four-talker babble and HINT noise speech recognition performances for the Noise Front, Noise Right conditions, and the spatial advantage measures. Significant relationships (p < 0.05) were found between masking noise performances for the Noise Left condition and the Noise Composite scores. CONCLUSIONS: One cannot assume that a patient who performs within normal limits on a speech in four-talker babble test will also perform within normal limits on a speech in steady-state speech-shaped noise test, and vice-versa. Additionally, performances for the Noise Front condition cannot be used to predict performances for the Noise Side conditions. The utilization of both HINT noise and four-talker babble maskers, with and without the spatial separation of the stimuli, may be useful when determining the range of speech recognition in noise abilities found in everyday listening conditions.
