Verbal disaster warnings and perceived intelligibility, reliability, and urgency: The effects of voice gender, fundamental frequency, and speaking rate

Abstract

In this paper, we study the effects of acoustic characteristics of spoken disaster warnings in Japanese on listeners' perceived intelligibility, reliability, and urgency. Our findings are threefold: (a) For both speaking speed and f_o, setting them to normal (compared from slow/fast ({+}/{-}20%) for speed, and from low/high (+/- up to 36 Hz) for f_o) improved the average evaluations for Intelligibility and Reliability. (b) For Urgency only, setting speed to faster (both slow to normal and normal to fast) or setting f_o to higher (both low to normal and normal to high) resulted in an improved average evaluation. (c) For all of intelligibility, reliability, and urgency, the main effect of speaking speed was the most dominant. In particular, urgency can be influenced by the speed factor alone by up to 39%. By setting speed to fast (+20%), all other things being equal, the average perceived urgency raised to 4.0 on the 1–5 scale from 3.2 when the speed is normal. Based on these results, we argue that the speech rate may effectively be varied depending on the purpose of an evacuation call, whether it prioritizes urgency, or intelligibility and reliability. Care should be taken to the possibility that the respondent-specific variation and experimental conditions may interplay these results.