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Re: Question on defining S/N ratio in speech-in-noise testing

It's a tricky issue. If one doesn't exclude gaps (silences) between words/sentences, the calculated SNR will likely underestimate the actual SNR. On the other hand, completely excluding the noises in such gaps will likely overestimate the actual SNR since these noises do have an adverse impact on target speech due to forward masking effects.

In a recent intelligibility study on normal-hearing and hearing-impaired listeners, we count the noise within the 100-ms period before a speech onset in our SNR calculations (see Sect. III.A.1, JASA 125, pp. 2336-2347, 2009).


Leonid Litvak wrote:
Hi All,

I have a question regarding definition of signal-to-noise ratio as it applies to speech-in-noise testing, with speech material being sentences. On a simple level, SNR is just level of the signal divided by the level of the noise.

The signal is typically speech, so its level fluctuates over time. Do people typically use the average signal level computed over the whole sentence, average signal level computed in 100 ms windows, medium signal level, maximum signal level, etc.?

The same question could go for the noise token as well.

I would very much appreciate references to papers that discuss these issues.

Finally, we are interested to apply these tests to cochlear implant recipients that have a well-characterized pre-emphasis curve as part of their processor. Should the pre-emphasis curve be taken into account when computing S/N ratios? This is not an issue for spectrally-matched noises, but may be an issue for non-matched noises.

Thank you very much!


Prof. DeLiang Wang
Department of Computer Science and Engineering
The Ohio State University
2015 Neil Ave.
Columbus, OH 43210-1277, U.S.A.

Phone: 614-292-6827 (OFFICE); 614-292-7402 (LAB)
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URL: http://www.cse.ohio-state.edu/~dwang