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EBP Compendium: Summary of Systematic Review

Efficacy of Directional Microphone Hearing Aids: A Meta-Analytic Perspective

Amlani, A. M. (2001).
Journal of the American Academy of Audiology, 12(4), 202-214.

Indicators of Review Quality:

The review addresses a clearly focused question Yes
Criteria for inclusion of studies are provided Yes
Search strategy is described in sufficient detail for replication Yes
Included studies are assessed for study quality Yes
Quality assessments are reproducible No

Description: This is a meta-analysis of published and unpublished studies investigating the efficacy of commercially available directional microphone hearing aids (DMHAs) for individuals with hearing impairment.

Question(s) Addressed:

  1.  Do DMHAs provide a beneficial signal-to-noise ratio (SNR) independent of such factors as environmental acoustics, type of speech stimulus, noise azimuth, hearing aid characteristics and microphone configuration?
  2. Does digital signal processing (DSP) provide an improvement in SNR relative to analog signal processing? If so, is this improvement dependent on microphone configuration?
  3. Is the amount of SNR improvement, if any, influenced by the use of certain noise stimuli and/or azimuth or origination?

Population: Hearing-impaired (HI) listeners.

Intervention/Assessment: Commercially available in-the-ear or behind-the-ear DMHAs.

Number of Studies Included: 18

Years Included: Not stated



  • "Overall, DMHAs were found to provide a statistically significant advantage over ODHAs in improving SNR when data are pooled across all variables" (pp. 211-12).
  • There is a "significant difference between ODHA and DMHA devices and listener groups [p < .05] but only in the less reverberant condition…higher reverberant conditions have been shown to affect the directionality of DMHAs, making them essentially omnidirectional…energy in the reverberant room increases and may even exceed the intensity of the target signal…reflected energy may change some of the characteristics important for speech intelligibility…" (p. 212).

Keywords: Directional Microphones, Hearing Aids

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Added to Compendium: December 2011

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