Abstract
The Lombard effect describes the automatic and involuntary increase in vocal intensity that speakers exhibit in noisy environments. Literature studying the Lombard effect has typically focused on the role of audition. Interestingly, previous studies of discrete, repetitive finger forces have noted similar automatic and involuntary increases in output, when visual feedback of force level is removed, which have been attributed to mechanisms of sensory attenuation affecting perceptions of self-generated somatosensory feedback. In two experiments we tested the hypothesis that sensory attenuation mechanisms also underlie the Lombard effect. First, we sought to replicate the Lombard effect using a repetitive vocalization task developed as a vocal analog to previous studies of repetitive force production (cf. Therrien, Richardson & Balasubramaniam, 2011). Second, we studied the role of somatosensory feedback in vocal intensity control by having participants perform the same repetitive vocalization task while auditory and visual feedback stimuli were manipulated. We hypothesized that providing a visual reference of participants' voice level would serve to calibrate somatosensory-based judgments of vocal intensity and result in reduced expression of the Lombard effect when auditory feedback was masked. Results confirmed our hypothesis, suggesting a prospective role for sensory attenuation mechanisms in situations where force production extends beyond discrete motor output.
