BKB-SIN
What is SNR Loss?

SNR loss is the increased signal-to-noise ratio required by a listener to understand speech in noise, as compared to normal performance. On the BKB-SIN Test normal-hearing adults obtain 50% correct at a -2.5 dB SNR. We call this the SNR-50. A hearing- impaired adult with an SNR-50 score of 7.5 dB would have a 10 dB SNR Loss [7.5 - (- 2.5) = 10]. The measurement of SNR loss is important because it cannot be reliably predicted from the pure tone audiogram.

Performance on any speech-in-noise test is affected by a number of factors, including:

  • Speech materials (sentences, spondees, etc.)
  • Background noise (shaped noise, multi-talker babble)
  • Test setup (combined speech and noise vs. separated speech and noise)
  • Audibility of the signal
  • Reverberation
  • Knowledge of the language
  • Subject age
Due to these factors, absolute scores for an individual subject will vary across different speech-in-noise tests. BKB-SIN Test scores are reported in SNR Loss because it is substantially independent of calibration and test material. Calibration and/or test material differences that affect SNR-50 values equally for normal and hearing-impaired listeners will "cancel out" in the SNR Loss calculation.

Knowing the SNR loss allows the hearing professional to recommend the appropriate technology (e.g., omni-directional microphones, directional microphones, array microphones, FM systems) required for the listener to function in noisy situations. Knowing the SNR loss also enables the hearing professional to give the patient realistic expectations for their potential improvement in noise with a given technology, which often reduces unnecessary visits for hearing aid re-adjustments after the fitting.

Interpreting test results for children should be done on a case-by-case basis. Results should not be interpreted in isolation, but rather be integrated with other information regarding a child's speech/language abilities, educational performance and ability to function in the classroom. See "Test Interpretation (children)" in the BKB-SIN Test manual for more information.

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