The influence of linguistic content on the Lombard effect.

PURPOSE The Lombard effect describes the tendency for speakers to increase pitch, intensity, and duration in the presence of noise. It is unclear whether these modifications are uniformly applied across all words within an utterance or whether information-bearing content words are further enhanced compared with function words. In the present study, the authors investigated the influence of linguistic content on acoustic modifications made to speech in noise. METHOD Sixteen speaker-listener pairs engaged in an interactive cooperative game in quiet, 60 dB of multitalker noise, and 90 dB of multitalker noise. Speaker productions were analyzed to examine differences in fundamental frequency (F(0)), intensity, and duration of target words in sentences across noise conditions. RESULTS Proportional increases in F(0,) intensity, and duration were noted for all word types as noise increased from quiet to 60 dB. From quiet to 90 dB, content words that referred to agents, objects, and locations were disproportionately elongated compared with function words. Additionally, agents were further enhanced by increased F(0). CONCLUSIONS At moderate noise levels, most word types appear to be uniformly boosted in F(0), intensity, and duration. As noise increases, linguistic content shapes the extent of the Lombard effect, with F(0) and duration serving as primary cues for marking information-bearing word types.