How to time-align correlated wav.files

Hello,

I am a music-technology student and new to Matlab. For my graduation project i need a script to automatically time-align and layer impuls responses (audio, wav). The files are all nearly identical (let's say 90% correlated)

What i need exactly:

-I have 20 impuls responses (.wav, mono) of 2 seconds (saved on my computer by another program)

-need Matlab to: 

*      Automatically import the files
*      Find the delay between the 20 correlated files
*      Layer them to 1 new audiofile (normalized, so it won't clip)
*      Save the audio file

I think i need xcorr in a recursive way?

Maybe it's a lot to ask, but i hope someone can give me a headstart. I am very motivated to learn more, but the clock is ticking and this is not my main profession.

Thanks a in advance

Answer 1

[Von Duesenberg]

This is homework so perhaps I can try to give you a couple of hints without providing you with the final solution. To import your files automatically, you'll probably need to loop through a list of your files and open them with audioread. To find the delay, yes, xcorr, or finddelay or alignsignals from the Signal Processing Toolbox should do the trick. Now I'm not sure what "layer" means in this case, but it probably refers to mixing your files, in other words, it's a simple addition. And if your signals have different sizes, you may want to zero-pad some of them, e.g. with padarray. Now this will cause your signal to clip (go above + 1 or below - 1), so you want to resize your final signal between these two values. And finally the audiowrite function will let you write your signal as a sound file.

[Walter Roberson]

Sometimes time-aligning refers to using Dynamic Time Warping https://www.mathworks.com/help/signal/ref/dtw.html

[Von Duesenberg]

Yes, I forgot to mention this option. In all cases, a visual check with simple plots is necessary because when signals are too different (which doesn't seem to be the case here), DTW can lead to funny solutions.

[harrie houthakker]

Thanks so much, Von Duesenberg and Walter

As i said, i am new to Mathlab, so maybe i'm gonna need a little more help on something specific, but i gonna try to figure it out with the tips you provided.

Cheers!

[harrie houthakker]

as expected, i do need some help.

I made a for-loop to use xcorr. But how can i recall my .wav files in a better way? So with every loop i process the next .wav file?

[ir1,Fs] = audioread('1ir.wav');
[ir2,Fs] = audioread('2ir.wav');
[ir3,Fs] = audioread('3ir.wav');

n = 2;

ir = zeros(1, 10);

for k = 1:n
        k

          if (k == 1);
              irx = ir2;
          elseif (k == 2);
              irx = ir3;
          end

          [acor,lag] = xcorr(ir1,irx);

          [~,I] = max(abs(acor));
          lagDiff = lag(I)
  end

thanks in advance!!

[Walter Roberson]

http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F