Effects of task and language nativeness on the Lombard effect and on its onset and offset timing

This study focuses on the differences in speech sound pressure levels (here, called speech loudness) of Lombard speech (i.e., speech produced in the presence of an energetic masker) associated with different tasks and language nativeness. Vocalizations were produced by native speakers of Japanese with normal hearing and limited English proficiency while performing four tasks: dialog, a competitive game (both communicative), soliloquy, and text passage reading (noncommunicative). Relative to the native language (L1), larger loudness increments were observed in the game and text reading when performed in the second language (L2). Communicative tasks yielded louder vocalizations and larger increments of speech loudness than did noncommunicative tasks regardless of the spoken language. The period in which speakers increased their loudness after the onset of the masker was about fourfold longer than the time in which they decreased their loudness after the offset of the masker. Results suggest that when relying on acoustic signals, speakers use similar vocalization strategies in L1 and L2, and these depend on the complexity of the task, the need for accurate pronunciation, and the presence of a listener. Results also suggest that speakers use different strategies depending on the onset or offset of an energetic masker.