After Effects Radio Waves FX Initial Size
Generate radio waves on a solid, adjust settings so they're looking appropriate.

Drag the time cursor forward until the waves have expanded to the point where you want them to start.

Cut your layer using the alt + left square bracket ( alt + [ )
Drag your layer left until it is at the beginning of your comp.

Make a solid layer that goes between your radio waves layer and your mouse image.
Mask the solid to the same size as your mouse image.
Set the Track Matte on your radio waves layer to "Alpha Inverted"