What is SNR Loss?
SNR loss is the increased signal-to-noise ratio required by an individual to
understand speech in noise, as compared to normal performance. A normal-hearing
person requires about +2 dB SNR (target talker 2 dB louder than background
babble talkers) to correctly repeat 50% of the key words on the QuickSIN test.
We call this the SNR-50. A hearing-impaired person who requires the target
speech to be 12 dB higher than the noise to achieve a 50% correct score would
have a 10 dB SNR loss.
QuickSIN scores are reported in SNR loss because it is substantially independent
of calibration and test material. Calibration and/or test material differences
that affect the SNR-50 values equally for normal and hearing-impaired subjects
will "cancel out" in the SNR loss calculation.
SNR Loss Solutions
Hearing aids (regardless of the type of signal processing they use) cannot
improve the SNR for the most commonly encountered difficult listening
situation, i.e., when what the listener wants to hear is speech, and what the
listener doesn't want to hear is also speech. SNR improvement can be
provided by directional hearing aid microphones, array microphones, and FM
systems. The QuickSIN test can be used to determine which, if any, of these
technologies is appropriate for a given patient, as well as to counsel the
patient regarding realistic expectations from a given technology.