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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).
DeLiang
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!
Leo
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Prof. DeLiang Wang
Department of Computer Science and Engineering
The Ohio State University
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