Re: question about speech level

[Tony Miller <antonio.miller@xxxxxxxxx>]

Ali-

A common approach to your problem is to use the ITU Objective
Measurement of Active Speech Level (P.56).

Here is a PDF version of the standard:
http://www.itu.int/rec/T-REC-P.56-201112-I/en

Peter Kabal at McGill University has a nice discussion of the details
of the calculations here:
http://bellatrix.ece.mcgill.ca/Documents/Reports/1999/KabalR1999.pdf

"Speech activity measurement involves determining the fraction of time
that a signal contains
active speech and the speech level while speech is active. Knowledge
of the speech activity is
important in speech signal measurements. For speech data bases, it is
important to ensure that
undue leading and trailing non-speech be excised and that the speech
level be properly scaled
based on the peak signal level and the active speech level [1]. For
testing speech coders with
environmental noise, artiïcial test signals are created by adding
recorded background noise to
clean speech segments. The signal-to-noise ratio for such
speech-plus-noise signals is determined
as the ratio of the active level for the speech to the rms level for
the recorded noise."

Mike Brookes at Imperial College London provides a MATLAB
implementation in his speech processing toolbox (VoiceBox).
http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/doc/voicebox/activlev.html

I hope this helps.
-Tony

--
Tony Miller
Acoustic Systems Group
Cirrus Logic, Austin, TX
http://cirrus.com/en/company/


On Mon, Jul 23, 2012 at 4:45 AM, ali fallah <ali.fallah@xxxxxxxxx> wrote:
>
> Dear List
>
> For creating speech in desired level, I have an AC40 audiometer that produce speech signal in selected dB SPL from a wav file. The recordings has silent periods before and after speech signal. If  I delete silent periods before and after the speech signal, the sound intensity  that audimeter produce, will not change.  Now I want to prepare a mixture of speech and noise in optional SNR values in Matlab but the RMS value of speech signal depends on  silent gaps.
>
> I have two question about this: I want to know for speech signal that is nonstationary, how  desired level in dB SPL is set . Also how can I mix speech and noise in Matlab by setting noise in desired value (for example noise level=65dBSPL and SNR=-10 until we have speech in 55 dBSPL).
> I will grateful if anyone guide me about this and let me know about related documents.
>
> best regards