SPATIAL PERCEPTION OF SPEECH IN VARIOUS SIGNAL-TO-NOISE RATIOS

Objective: The study was designed to assess the effects of background noise level on the detection and localization of speech. Design: The p hrase ''Where is this?'' was presented either in quiet or in a diffuse noise field, through loudspeakers arranged in a 360 degrees azimuth a rray. The noise conditions included 11 signal to noise ratios (SNRs) r anging from -18 dB SNR to +12 dB SNR in 3 dB increments. Seventeen nor mal-hearing subjects, aged 18 to 29, participated in the study. Result s: Results revealed that in all listening conditions the signal was mo st easily detected when presented through a loudspeaker positioned at 90 degrees or 270 degrees azimuth. Although the actual level for 50% d etection varied as a function of loudspeaker location and SNR, 85% and 100% of all presentations of the signal were detected at -9 dB and -6 dB SNR, respectively. Localization accuracy improved as the SNR incre ased, ranging from 18% accuracy at -18 dB SNR to 89% at +12 dB SNR, Lo calization accuracy in quiet was 95%. The data are discussed in refere nce to patterns of responses at each loudspeaker location.Conclusions: Detection of the target signal deteriorated as background noise level increased and was dependent on the source location of the incoming si gnal, as expected. Localization accuracy of the target signal was high ly dependent on the SNR and spatial location of the signal source. Det ection and localization accuracy data were found to be repeatable acro ss test sessions and response patterns were found to be symmetrical on the right and left sides of the horizontal plane.