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The effect of head-induced interaural time and level differences on speech intelligibility in noise
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1988
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Acoustic HeadshadowPsychoacousticsCognitive ScienceSpatial AudioLevel DifferencesHealth SciencesEngineeringAuditory ModelingSpeech IntelligibilitySpeech Reception ThresholdsNoiseHead-induced Interaural TimeSpeech ProcessingInteraural Time DelaySpeech PerceptionSpeech CommunicationSpeech Recognition
The study examined how interaural time delay and acoustic headshadow affect binaural speech intelligibility in noise. Researchers simulated free‑field listening with a KEMAR manikin, recorded speech and noise from seven azimuths, extracted ITD‑only and ILD‑only signals, and measured speech‑reception thresholds in normal‑hearing listeners, including a second experiment with simulated hearing loss and fixed‑ITD noise. ITD provided a 3.9–5.1 dB gain and ILD a 3.5–7.8 dB gain for noise azimuths 30–150°, but ILD reduced binaural unmasking, lowering the average threshold shift from 4.6 to 2.6 dB. Abstract truncated at 250 words.
A study was made of the effect of interaural time delay (ITD) and acoustic headshadow on binaural speech intelligibility in noise. A free-field condition was simulated by presenting recordings, made with a KEMAR manikin in an anechoic room, through earphones. Recordings were made of speech, reproduced in front of the manikin, and of noise, emanating from seven angles in the azimuthal plane, ranging from 0 degree (frontal) to 180 degrees in steps of 30 degrees. From this noise, two signals were derived, one containing only ITD, the other containing only interaural level differences (ILD) due to headshadow. Using this material, speech reception thresholds (SRT) for sentences in noise were determined for a group of normal-hearing subjects. Results show that (1) for noise azimuths between 30 degrees and 150 degrees, the gain due to ITD lies between 3.9 and 5.1 dB, while the gain due to ILD ranges from 3.5 to 7.8 dB, and (2) ILD decreases the effectiveness of binaural unmasking due to ITD (on the average, the threshold shift drops from 4.6 to 2.6 dB). In a second experiment, also conducted with normal-hearing subjects, similar stimuli were used, but now presented monaurally or with an overall 20-dB attenuation in one channel, in order to simulate hearing loss. In addition, SRTs were determined for noise with fixed ITDs, for comparison with the results obtained with head-induced (frequency dependent) ITDs. (ABSTRACT TRUNCATED AT 250 WORDS)