How do you concatenate two audio files horizontally? (.WAV)

I'm trying to merge two .WAV files together so that they can be played at the same time.

The problem is they may be of different frequencies as one may be a voice recording. I've learnt how to concat vertically but require some insight into the process of concatenating two separate audios horizontally.

Any help would be appreciated.

Answer 1

[Walter Roberson]

[wav1, Fs1] = audioread('RockGuitar.wav');
[wav2, Fs2] = audioread('guitartune.wav');

maxFs = max(Fs1, Fs2);
rs1 = resample(wav1, maxFs, Fs1);
rs2 = resample(wav2, maxFs, Fs2);
maxlength = max(size(rs1,1), size(rs2,1));
rs1(end+1:maxlength,:) = 0;
rs2(end+1:maxlength,:) = 0;
horizontal_wav = [rs1, rs2];

size(horizontal_wav)

ans = 1×2

3195904 3

p = audioplayer(horizontal_wav(:,end-1:end), maxFs);
play(p)

You are going to need more work to be able to play the 3 or 4 channels simultaneously. Note that the channels have not been processed for Dolby Surround or Dolby DTS, but you could use them for front and back speakers, for example.

Remember to pay attention to the fact you are not promised that they are all the same number of channels, so horizontal concatenation like you asked for loses the boundaries between which channel came from which sound.

... And you did not ask to play them as separate stereo channels, and you did not ask that the respective channels be mixed together.

[dan bloodworth]

Thank you for this, this is really helpful so far!

How would it be possible to play them on separate stereo channels/mixed together?

[Walter Roberson]

To play them on separate stereo channels, you have to take the mean() of each across the second dimension in order to mix them down to a single channel each, before you concatenate them horizontally.

[dan bloodworth]

Is there any examples/documentation I can read to help me with this?

[Walter Roberson]

https://www.mathworks.com/help/matlab/ref/mean.html

https://www.tunecore.com/blog/2020/02/the-difference-between-mixing-in-mono-vs-stereo-part-1.html

[dan bloodworth]

Thank you sir