Speech perception in noise: Directional microphones versus frequency modulation (FM) systems

Approximately 29 million individuals in the United States today have some degree of hearing impairment. The major consequence of hearing impairment is communicative difficulty, especially in adverse listening environments. The purpose of this investigation was to examine the speech perception in noise ability of adults with sensorineural hearing loss under various listening conditions. Specifically, speech perception was assessed on 22 adults with slight to severe sensorineural hearing loss under the following listening conditions: (1) unaided; (2) binaural hearing aids in the omnidirectional microphone mode; (3) binaural hearing aids in the directional microphone mode; (4) binaural hearing aids utilized with one FM receiver in the FM only mode; (5) binaural hearing aids utilized with two FM receivers in the FM only mode; and (6) binaural hearing aids utilized with two FM receivers with the environmental microphone equalized to the FM signal (FM + M mode). Speech perception in noise was assessed via the Hearing In Noise Test (HINT) sentences using an adaptive procedure. The HINT sentences were presented via a loudspeaker located at 0° azimuth. Speech spectrum shaped noise served as the noise competition. This noise was presented at a level of 65 dB SPL from four loudspeakers located at 45°, 135°, 225°, and 315° azimuths.; Results revealed that all aided listening conditions resulted in a significant improvement in speech perception over the unaided listening condition. As with previous studies, binaural hearing aids in the directional microphone mode outperformed binaural hearing aids in the omnidirectional microphone mode. The listening conditions in which the FM system was utilized resulted in significantly better speech perception performance than any of the hearing aid alone conditions. Additionally, these listening conditions with the FM system resulted in significantly better speech perception performance than that obtained by listeners with normal hearing (without amplification) in the same listening environment. The condition in which two hearing aids were used in conjunction with two FM receivers in the FM only mode resulted in the best speech perception performance overall. Implications of these results on audiologic practice are discussed.