Re: Export Wav file calibration (Tony Miller )

Subject: Re: Export Wav file calibration
From:    Tony Miller  <antonio.miller@xxxxxxxx>
Date:    Thu, 26 Jan 2012 10:28:06 -0600

Bruce- The Loudness Toolbox assumes your inputs to the functions are in Pascals. Here is a simple check that one of the wavefiles labeled as 60dBSPL in the Loudness_Validation.m script, uses this calibration convention and is, in fact, 60dBSPL. [Tone_1kHz_60dBSPL,fs,bits] = wavread(fullfile('WAV','ToneBurst_1000Hz_60dBSPL_200ms.wav')); Verify_Tone_dBSPL = 20*log10(sqrt(var(Tone_1kHz_60dBSPL(1000:8000)))./20e-6) Verify_Tone_dBSPL = 59.9960 In MATLAB, any vector you send to one of the loudness functions should use this convention (1 Pa = 94dBSPL). When you input your 94dBSPL calibration tone as a time series to the loudness functions, please verify that the RMS value is 1. If it isn't, then you need to multiply by a scale factor so that your RMS value is 1. Also, it's important to make sure you are taking the RMS of only the steady state portion of the signal, hence the use of only a portion of the file in the above example, Tone_1kHz_60dBSPL(1000:8000). I hope this helps. -Tony -- Tony Miller Acoustic Systems Group Cirrus Logic, Mixed Signal Audio Division 2901 Via Fortuna Austin, TX 78746-7574 On Wed, Jan 25, 2012 at 4:13 PM, Bruce Yao <bruce.yao@xxxxxxxx> 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

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