Quantifying the Lombard effect in different background noises

Abstract

The Lombard effect of increasing one’s vocal effort in the presence of background noise has been quantified by Pearsons et al. (1977) as a 0.6-dB increase in speech levels for each dB increase in the background noise up to a ceiling level. Lombard speech has also been investigated in other studies with variable results. This study reports data on the effect of different noises on (1) the slope of the function relating speech levels and noise levels and (2) the spectral structure of speech. Twenty normal-hearing adults were asked to read aloud ten sentences from the hearing in noise test (HINT) to an experimenter seated 1 m away, in quiet and in various noises (white, speech spectrum, babble, and restaurant) presented in the sound field at 60 and 75 dBA. Preliminary findings show that increases in speech levels in natural environmental noises (restaurant and babble) most closely follow Pearsons’ data, with a slope of 0.6 dB. In contrast, artificial noises (speech spectrum and white) were associated with lower slopes (0.2 and 0.4 dB, respectively). Findings of this study could be useful in a wider context of modeling the complete speech communication process from talker to listener.