SPL of wav file

Hello I have several different recordings of a piano and I wish to calculate the mean SPL over all frequency bins to get a single number for each wav recording level. I am totally new to Matlab and could do with some advice.

Answer 1

[Binaya]

Hi Ryan

I understand that you want to calculate mean SPL i.e. Sound Pressure Level for all frequency bins in a recorded file.

To calculate the SPL we need the amplitude of the audio signal at each frequency level which can be obtained from the frequency representation of the signal like Fourier transform, Laplace transform.

You can use the "fft" function to calculate the Fourier Transform of the given audio signal. Once the Fourier Transform is calculated you can use the following code snippet to calculate the mean SPL:

N = length(audioData)
Y = fft(audioData); % Compute the FFT
P2 = abs(Y/N); % Two-sided spectrum
P1 = P2(1:N/2+1); % Single-sided spectrum
P1(2:end-1) = 2*P1(2:end-1); % Correct the amplitude
p_ref = 20e-6;
% Calculate SPL
SPL = 20 * log10(P1 / p_ref);
% Compute the mean SPL
meanSPL = mean(SPL);

Similarly, you can find the sound pressure level for all audio files.

Hope this helps.