The COSI 17 or APHAB 18 also provide useful subjective indications regarding patient expectations for benefit from amplification. Table 2 illustrates how SNR loss for speech may, in turn, be used to develop candidacy guidelines for benefit from directional microphones and FM technology. Several researchers, including Mead Killion who is a strong advocate of directional microphone use, 14 have suggested that speech recognition in noise measures, such as the QuickSIN 15 or Hearing in Noise Test, 16 may be useful for determining an individual patients SNR deficit for speech. For example, the audiogram alone does not provide a good indication of the degree to which individual hearing aid patients have difficulty listening in background noise. 13įinally, it should be recognized that directional microphonesdespite their newfound popularitymay not be for everyone. Conditions included binaural omni-directional (Omni/Omni), fixed (Fixed/Fixed), and Adaptive broad-band directional (Adapt/Adapt), and "mismatched" omni/adaptive directional conditions (AdaptL/OmniR AdaptR/OmniL). Speech recognition thresholds (SRT) in noise for hearing aid users in "Matched" and "Mismatched" hearing aid conditions. Given that 77% of all US hearing aid fittings are binaural, 7 this topic has the potential to impact many hearing aid users.įIGURE 9. The clinical implications are that, for asymmetric environmental noise conditions, it may be preferable not to synchronize microphone mode across ears for directional microphone systems. Customer satisfaction with value, benefit in noise, overall benefit, and likelihood of repurchasing current brand of hearing instrument (hearing instruments R and R>L). 6 Directional microphone use did not increase appreciably in the US, however, until they were adapted for use with in-the-ear (ITE) hearing aids.įIGURE 1. 5 were among the first to report benefit for subjects wearing behind-the-ear (BTE) directional microphone hearing aids in a randomized, controlled study, and as a result, Phonak received FDA approval for the claim of improved speech recognition in noise. 4 It is therefore somewhat surprising that directional microphone usage in hearing aids remained low until the mid-1990s, when most directional systems offered the ability to switch between the omnidirectional and directional modes, and the FDA began to require substantiation for speech-in-noise claims made by manufacturers. 1 In 1984, Hawkins & Yacullo 2 reported a 3-4 dB signal-to-noise ratio (SNR) advantage with directional microphone hearing aids in hard-of-hearing listeners (compared with omni-directional microphone hearing aid performance), and Dillon & Macrae 3 also reported a similar benefit in that year.Ībundant evidence suggests that hearing aid users frequently report that satisfaction decreases as background noise increases. In fact, directional microphones were first used 60 years ago to help prevent acoustic feedback in public address systems and suppress noise at sporting events, and directional microphones in hearing aids have been available in the United States since the early-1970s. Directional microphone technology is not new.
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