What is the amplitude unit when we plot wav. files?

Hello, I work with bioacoustics and in my analysis I usually use softwares like Raven 1.4 and Adobe Audition. However, I've been urged to apply Matlab in my analysis.

I need to calculate underwater sound pressure levels. I usually take the values provided by Adobe (in dBFS) and perform the necessary conversions and calculations to obtain SPL. In Matlab I need to what is the amplitude unit when I open wav. files.

Can I calculate SPL directly from the wav. file using the amplitude levels and calibration data or do I need to insert a calibration file separately?

Thank you, Lis

Answer 1

[Walter Roberson]

Usually wav files are 0 to 255, or -1 x < 1 (notice that is not '<=' 1). See <http://www.mathworks.com/help/matlab/ref/wavwrite.html

[Lis]

Thank you for reading my question. I understand that the amplitude range is –1.0 <= y <= +1.0. What I would like to know is if the values contained in this range are voltage values or if they are a normalized plot of voltage values that must be converted before the SPL calculation.

Lis

[Walter Roberson]

They are normalized, with -1 to correspond to the minimum voltage that can be produced by the line driver, and +1 to correspond to the maximum voltage that can be produced by the line driver.

Answer 2

[Daniel Shub]

Wav files come in two varieties. The first has a range -1 to 1 and the second has the range 0 to 255. For the first 20*log10(x) corresponds to dB FS while for the second 20*log10((x-128)/255) gives dB FS.

[Zhuoyi Ma]

You forgot to divide the x by P0= 20e-6

[Mohammed Alkhatib]

he is right you are wrong. he said its dB FS in that case you dont need to divide but if its dBSPL then you have to divide by P0