The Lombard effect in muscle tension dysphonia: mechanistic and clinical characterization

Project Summary
The objective of this project is to investigate voice changes associated with speaking in challenging acoustic
environments to better inform clinical care for individuals with voice disorders. Muscle tension dysphonia (MTD)
is a common voice disorder that often results in difficulty communicating in daily life. Many people experience
voice symptoms from speaking in noisy environments; for most, the symptoms resolve quickly. However, for
those with MTD, voice symptoms often persist, making it difficult for them to meet their occupational and social
vocal demands. The reasons for this persistence are unknown. Therefore, it is essential to elucidate the
underlying mechanisms of voice production in noisy environments to optimize and individualize voice
assessment and treatment for these individuals with MTD. Most speakers increase their vocal intensity while
speaking in noisy environments, a phenomenon known as the Lombard effect. Speaking during and after
exposure to a loud environment presumably requires monitoring of both background noise and one’s own voice,
and then responding with vocal motor adjustments. This implies that sensorimotor integration is crucial in these
real-life circumstances. There is preliminary evidence that individuals with MTD have atypical auditory-motor
integration and an atypical persistence of Lombard responses after speaking in noise. However, no known
studies have comprehensively characterized the underlying mechanisms and clinically relevant voice changes
of the Lombard effect for those with and without MTD. To develop evidenced-based diagnostics and targeted
voice treatments, we must better understand the processes and voice changes associated with speaking in daily
life. Therefore, the specific aims of this project are to 1) investigate the sensorimotor mechanisms of the Lombard
effect and 2) characterize clinically relevant voice changes associated with the Lombard effect for individuals
with and without MTD within a communicative context. Sixty speakers (30 with MTD and 30 without) will complete
a Lombard task to measure vocal responses and self-reported vocal effort while communicating during and after
exposure to a noisy environment. Inexperienced listeners will rate overall severity of dysphonia for the speakers’
speech samples from the Lombard task. Lombard responses will be analyzed behaviorally and neuro-
computationally, and they will be compared between the groups and across various stages of the Lombard task.
Clinically relevant vocal measures (i.e., acoustic, self-reported vocal effort, and listener-auditory perceptual
ratings of overall severity of dysphonia) of the Lombard task will be compared across groups and phases of the
experimental task. This project is theoretically and clinically significant; it will fill in a substantial gap, providing
theoretical insight into the sensorimotor mechanisms of MTD in real-life environmental contexts, and contributing
to the clinical evidence to improve diagnostics and individualize treatment for those with sensorimotor deficits
underlying their voice disorders.

Grant Number: 5F31DC021863-02
NIH Institute/Center: NIH
Principal Investigator: Allison Aaron