A PROCEDURE FOR TESTING SPEECH-INTELLIGIBILITY IN A VIRTUAL LISTENINGENVIRONMENT

Objective: The development of a test of virtual speech intelligibility in noise that enables assessment in typical, everyday listening situa tions. To eliminate extraneous confounding factors, digital signal pro cessing was incorporated to simulate listening environments and source locations and allow presentation of stimuli via earphones. Design: So urce-to-eardrum transfer functions measured on KEMAR for various sourc e locations in anechoic and reverberant environments were used to proc ess monosyllabic words and speech-spectrum noise. Speech intelligibili ty was measured for three speech and noise configurations in two envir onments using an adaptive procedure to determine the signal-to-noise ( S/N) ratio for 50% intelligibility. Results: Normal-hearing listeners achieved 50% intelligibility of monosyllabic words at significantly lo wer S/N ratios in a virtual anechoic environment than in a virtual rev erberant environment. Speech intelligibility improved significantly in both environments when the speech and noise sources were separated, b ut the intelligibility gain in the anechoic environment was four times larger than in the reverberant environment. Conclusions: This test is easy to administer and score, and it provides a means for measuring: 1) the effects of separating speech and noise sources and 2) the effec ts of reverberation on speech intelligibility in noise while eliminati ng confounding factors such as calibration.