Talker-to-listener distance effects on speech production and perception.

Simulating talker-to-listener distance (TLD) in virtual audio environments requires mimicking natural changes in vocal effort. Studies have identified several acoustic parameters manipulated by talkers when varying vocal effort. However, no systematic study has investigated vocal effort variations due to TLD, under natural conditions, and their perceptual consequences. This work examined the feasibility of varying the vocal effort cues for TLD in synthesized speech and real speech by (a) recording and analyzing single word tokens spoken at 1 m < or = TLD < or = 32 m, (b) creating synthetic and modified speech tokens that vary in one or more acoustic parameters associated with vocal effort, and (c) conducting perceptual tests on the reference, synthetic, and modified tokens to identify salient cues for TLD perception. Measured changes in fundamental frequency, intensity, and formant frequencies of the reference tokens across TLD were similar to other reports in the literature. Perceptual experiments that asked listeners to estimate TLD showed that TLD estimation is most accurate with real speech; however, large standard deviations in the responses suggest that reliable judgments can only be made for gross changes in TLD.