Attach sound to buttons

I have fifteen buttons in a movie, each with its own sound file. I linked each sound to its button thus:

on (release) {
btn_Adaptation = new Sound(this);

and each button works perfectly. However, the size of the movie increased by about 8,000KB. Is this normal? The combined file size of the sound files is about 1200KB. Does anyone know another way I should do this, to keep the size of the movie down?