# Long Term Average Spectrum of large batch of audio files

I'm trying to obtain the overall LTAS of a large batch of audio (wav) files. To do this, I should obtain the LTAS of each file individually, then take the average value across all LTASs for each frequency. I also need the standard deviation for each frequency. I'm doing this in Matlab, but am rather a noob. Can anyone offer any pointers to help me write a Matlab script to do this? Thanks!

## 2 Answers

1. use "wavread()" to read the audio files
2. use "pwelch()" to calculated the power spectrum of the songs
3. you do energy averagin over multiple songs.

Something like this (just a code sketch)

nx = 8192; % that's about 5 Hz @44.1 kHz
dd = dir('*.wav'); % all files in the current directory
nFiles = length(dd);
LTAS = zeros(nx/2+1,nFiles)
for i = 1:nFiles
x = wavread(dd(i).name);
LTAS(:,i) = pwelch(x,hanning(nx),nx/2);
end
LTASOverAllSongs = mean(LTAS,2);

• Thanks for your reply, Hilmar. I can't figure out what to do with the wavread - x = wavread(dd(i).name; - line, though. That's not how I've used wavread previously. Any suggestions? Thanks! – Nobbynomates Mar 3 '14 at 14:35
• It is simply reading the wav file listed previously by dd=dir('*.wav'); (all in current folder). Please mind that there is a missing bracket in this line, should be: x = wavread(dd(i).name). – jojek Mar 29 '14 at 20:12

I know this question is a few years old but here is a solution for the record:

LTASS.m function for MATLAB (Github)

(This is a similar solution to Hilmar's)(Note: Will require getAllFiles() function to work)

• Hi, can you explain further how to make "getAllfiles()_function" to work? I am very new to MATLAB and unsure how to solve this. Thanks! – rjh3m8 Jan 30 '20 at 21:10