Speech signal SPL & S/N

[Athanassios Protopapas <protopap@xxxxxxxxxxxxxxxxxxx>]

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From protopap Wed Mar 11 17:05:19 1998
Subject: Speech signal SPL & S/N
To: auditory@vm1.mcgill.ca
Date: Wed, 11 Mar 1998 17:05:19 -0800 (PST)
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Dear list:

I am looking for advice on calibrating sound pressure levels for speech
stimuli.  A friend has asked the following questions and my answer was
somewhere between "I'm not sure" and "it depends."  My impression is that
it's not possible to define precisely SPL for speech because of the pauses
and ever present amplitude changes over all time scales.   I would assume
that a long-term RMS might be the answer for sentence stimuli (but single
words will not be as simple), however imprecise.  I assume that people who
deal with speech intelligibility in noise, hearing aids, and all those
other cases where S/N values are calculated for speech signals would be
able to enlighten us.

Thank you in advance,

Thanassi Protopapas


>
>Questions:
>
>--What is the best way to control and calibrate sound-pressure levels
>during stimulus presentation across speech stimuli?  (I've read about
>peak-to-peak estimated dB SPL--what is this and how do I do it?)
>
>--What is the best way to apply the maskers?  Should I use noise
>generators, or generate the noise digitally and mix it with my digital
>speech signal?  If I do it digitally, what software (and by extension what
>operating system) would be best suited for the job?
>
>--What is the best way to determine S/N ratio?  Should I use rms amplitude?
>Over what portion of the signal?  Again, what software will allow me to do
>this most efficiently?