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Signal Noise Ratio (SNR) is the ratio between the desired information signal (speech) and the undesired signal (background noise). A higher SNR indicates that speech will be better understood (a better signal-to-noise ratio). The SNR needed by an individual depends on the specific environment, the task, and the individual.

An example of low SNR. If you’re purchasing an item at a noisy retail counter, it may be difficult to understand the sales associate (signal) ‘above’ the talking by other customers and environmental sounds (noise).

SNR is expressed in decibels (dB).

  • Hearing instruments increase SNR up to 6 dB.
  • Assistive listening systems increase SNR up to 30 dB.
  • See a graph that compares hearing aid SNR to assistive listening SNR in different environments.

A related term: SNR-Loss. Loss in the ability to understand speech at the signal-to-noise used by those with typical hearing regardless of the volume level. SNR-Loss must be evaluated with a Speech-in-Noise test and is independent of the loss of sensitivity – or the hearing threshold in dB.

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