Speech intelligibility in noise using throat and acoustic microphones

Abstract : Rotary-wing aircraft crew are exposed to high levels of ambient noise that can cause hearing loss and impede speech communication. Existing technology generally focuses on the listener and devices that can increase the signal-to-noise ratio and decrease noise-induced hearing loss. However, speech intelligibility is still dependent on the quality of the original speech signal. Throat microphones greatly reduce ambient noise in the original signal, thus enhancing the signal-to-noise ratio for the listener, but higher frequencies are eliminated which may negatively affect speech intelligibility. Speech intelligibility for signals generated by an acoustic microphone, a throat microphone, and the two microphones together was assessed using the Modified Rhyme Test (MRT). Stimulus words were digitally recorded in a reverberant chamber with broadband noise intensity at 90 dB(A) and 106 dB(A). Listeners completed the MRT task in the same seflings, thus simulating typical environments of a rotary-wing aircraft. Results show that speech intelligibility is much worse for the throat microphone than for the acoustic microphone, particularly for the higher noise level. In addition, no benefit is gained by adding the throat microphone signal to the acoustic microphone signal.