Multiple sounds played simultaneously

I have 2 or 3 sounds played in GUI by button. When I push it for the first time sounds aren´t simultaneous.

But when I push the same button for the second time(without closing the app), sounds play at once.

Can anybody tell me why and help me to fix it? I want them to be played at once from the first push.

This is part of my code.. may help.

function HraButton_3Pushed(app, event)

load gong.mat;
fs = 8000;
dt = 1/fs;
t = (0:dt:1);
y1 = sin(2*pi*b1*t);
y2 = sin(2*pi*b2*t);
y3 = sin(2*pi*b3*t); %b1,b2,b3 are some selected frequencies

sound(y1,fs)
sound(y2,fs)
sound(y3,fs)  

end

Thank youuuu!

Answer 1

[Walter Roberson]

sound() never guarantees synchronization.

The first time in a session that you use sound(), it takes time to initialize and start playing. The second time, some of the initialization is already done.

You should be using a single sound() call with the mean() of all of the tones you want to play at the same time.

[Erika Dubajova]

Okey, thanks a lot.