Effects of delay time and intensity difference on recognition of overlapped speech sound

Abstract

Speech sound transmitted from an outdoor loudspeaker is sometimes difficult to recognize because it is overlapped by a time-delayed speech sound from other loudspeakers. This difficulty is assumed to depend on a delay time and an intensity difference between the original and overlapping time-delayed sounds. To clarify the effects of a delay time and an intensity difference on speech recognition, a listening experiment was conducted with 21 Japanese adults using 105 Japanese spoken words in a carrier sentence, with delay times and intensity differences ranging between 0–250 ms and 0–9 dB, respectively. The experiment revealed that recognition ratios are significantly lower for delay times of 100–250 ms than for 0 ms. Similarly, the ratios are significantly lower for intensity differences of 0–6 dB than for 9 dB. These results suggest that speech sound from an outdoor loudspeaker is difficult to recognize in a large area where the difference of distances from two loudspeakers ranges between 34 and 85 m and the intensity difference between the original and overlapping time-delayed sound is less than 6 dB. [This study was supported by JSPS KAKENHI Grant Numbers JP15K12494, JP15H03207, JP17K02705, and by Aichi-Shukutoku University Cooperative Research Grant 2017-2018.]