Communications in Severe Low-Frequency Noise: An Investigation of Microphone Type and Speech Level on Intelligibility and Attenuation

Abstract

Severe (114 dBA) low-frequency-biased noise, characteristic of military tracked vehicles, was used to examine the speech intelligibility and cognitive effects of at-ear noise reductions provided by contrasting microphone technologies. Using two communications microphones (hereafter, “CommMicl and CommMic2”) intended for U.S. Army tank crew members, participants underwent Modified Rhyme intelligibility tests and Complex Cognitive Assessment Battery (CCAB) tests simultaneously in the noise environment while immersed in loading tasks. Results indicated that CommMic2 reduced the noise level at the ear by about 2 dB more than CommMicl. However, CommMicl yielded significantly better speech intelligibility at a 96 dB speech level. CCAB performance showed an increasing trend with higher speech levels for both communication microphones, but only significantly so for CommMicl. Speech level and communication microphone type did not have an effect on perceived mental workload.

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