Subject: Re: Export Wav file calibration From: Bob Masta <audio@xxxxxxxx> Date: Thu, 26 Jan 2012 08:30:43 -0500 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>
Note that the WAV file format does not include any provisions for encoding information like absolute level. It only holds A/D "counts", such that +/-32767 (2^15-1) is the peak-to-peak limit of a 16-bit card, or +/-8388607 (2^23-1) for a 24-bit card. Calibration information *can* be appended onto the basic WAV format to create a custom format such that the appended data will be ignored by programs that are not able to handle it, but there is no standard for this... the recording and analysis software need to use the same custom format. So, any absolute calibration that Matlab appears to have is an assumption on its part. I don't use Matlab, but presumably this is just a scale factor somewhere. Best regards, Bob Masta ================================= On 25 Jan 2012 at 17:13, Bruce Yao wrote: > Dear all, > > I have recently downloaded the loudness toolbox from Genesis because > of its capability of measuring N10 loudness from a wav file. > Our lab has a basic ArtemiS software that can record loudness level > but not N10 loudness. I was able to export a pure 94dB tone > (calibrated at 94dB) to wav and open it with the loudness toolbox. > But, the pressure(Pa) shown in MATLAB is not comparable to what I have > in ArtemiS. > After a few days of trial and error I found out that loudness toolbox > in MATLAB read the wav file with a pre-set 85dB calibration factor. > Since I can not scaled down the 94dB file to 85dB because of > overmodulation, is there a way for MATLAB to import the wav file with > 94dB calibration? > > Thanks in advance! > Best Regards, > Bruce Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!