Noise-management algorithm may improve speech intelligibility in noise

A likely consequence of sensorineural hearing loss is a diminished ability to understand speech in noisy backgrounds. Indeed, the inability to hear in noise is one of the main reasons for dissatisfaction with hearing aid use.1 Although hearing aids with a directional microphone provide substantial improvement in the ability of wearers to understand speech in noisy environments,2 space requirements and the uncertainty of directional characteristics when a directional hearing aid is inserted deeply into the ear canal prevent the implementation of such technology in the smallest completely-in-the-canal (CIC) hearing aids. A patient who insists on wearing CIC hearing aids will have to rely solely on the efficacy of single-mic noise-management strategies. Currently, most commercial “noise reduction” schemes use the modulation rates of the input signal as a basis for estimating the “speech” and “noise” nature of the input. “Speech” sounds are amplified with input-dependent gain, while “noise” sounds are typically amplified at a reduced gain level beyond input-dependent levels (see Chung, 20043). The exact amount of gain reduction and its time course vary greatly among manufacturers. Despite such differences, most studies have reported only an improvement in listening comfort by use of such a scheme.4 The improvement in listening comfort is noteworthy. It suggests that hearing-impaired persons whose hearing aids have noise reduction may be less affected by high-output sound pressure levels, less stressed, and less distracted in noisy situations, and may be more likely to attend to the sound sources and wear their hearing aids longer than if they lacked this feature. Wearers may also improve their participation in daily activities and their quality of life. It is possible that the reduction in stress level (or distractions) may improve the user’s speech understanding in some noisy environments.