Why Sounds in MATLAB (for example 'RockGuita​r-16-44p1-​stereo-72s​ecs.wav') contains two identical rows of matrix?

I'm curious why matrix of sounds in matlab contains two identical rows. For example when i use

[signal Fs] = audioread('RockGuitar-16-44p1-stereo-72secs.wav')

it contains two identical rows. And then when i do

soundsc(signal,Fs)

And compare it with

soundsc(signal(:,1), Fs)

It sounds no different (at least for me).

So why it need 2 rows then?

Thank you so much!

Answer 1

[Jonas]

there are two channels, one for the right speaker, one for the left (stereo). a mono signal would be one channel only, if you play the same values left and right it is stereo (because two channels are played) but it does not have the typical stereo experience like an instrument playing louder at one ear compared to the other. if you give Matlab only one channel of sound, it plays the same values at the left and right because otherwise it would have to decide on which channel to play. of you want to play a truly mono signal (sound only at one ear) you have to give matlab two channels, one with the sound, the other zeros only