Journal of the Acoustical Society of America volume:140:8-19.
When talkers speak in masking sounds, their speech undergoes a variety of acoustic and phonetic
changes. These changes are known collectively as the Lombard effect. Most behavioural research
and neuroimaging research in this area has concentrated on the effect of energetic maskers such
as white noise on Lombard speech. Previous fMRI studies have argued that neural responses to
speaking in noise are driven by the quality of auditory feedback—that is, the audibility of the
speaker’s voice over the masker. However, we also frequently produce speech in the presence of
informational maskers such as another talker. Here, speakers read sentences over a range of
maskers varying in their informational and energetic content: speech, rotated speech, speech
modulated noise, and white noise. Subjects also spoke in quiet and listened to the maskers without
speaking. When subjects spoke in masking sounds, their vocal intensity increased in line with
the energetic content of the masker. However, the opposite pattern was found neurally. In the
superior temporal gyrus, activation was most strongly associated with increases in informational,
rather than energetic, masking. This suggests that the neural activations associated with speaking
in noise are more complex than a simple feedback response.