The Effect of Unilateral Hearing Protection on Vocal Intensity With Varying Degrees of Background Noise

Abstract

The Lombard effect (LE) is a phenomenon in which speakers adjust their vocal production by raising the volume in noisy environments. As a result, the LE can create problems of vocal strain, fatigue and potential injury. This study aims to examine the difference in vocal intensity output in subjects wearing unilateral hearing protection versus no hearing protection in the presence of background noise. Each subject was seated inside a sound booth wearing a head-mounted microphone. Subjects were asked to read an excerpt from "The Rainbow Passage" while various levels of background noise were played: 50, 60, 70, and 80 dBA (Multitalker Babble). Each noise level was played while the subject was with and without unilateral ear protection (Optime 98 Earmuff [3M]) in random order. The earmuff has a noise reduction rating of 25 dB. After each reading of the text, subjects were asked to rate communication disturbance, vocal clarity, and discomfort during talking using a 10 cm visual analogue scale. The LE is reduced from 0.38 dB/dB to 0.29 dB/dB with unilateral ear occlusion. However, self-perception of disturbance, clarity and comfort were not affected by unilateral occlusion, only by noise level. Unilateral hearing protection reduces the LE and may protect against phonotrauma when speaking in an environment with loud background noise.