Cyber Stompin Optimus Prime battlemode sounds/how to?

[bilbo777]

Picked up a Cullen version. This is the non-transforming 10 inch toy with the gun left arm and launchable right arm. Got it mostly for the voice.

Anyone know about how to get this thing in 'battle mode'? Pressing the left side body button at waist only seems to silence the leg movement sounds from foot buttons. And have to hold the button down. Everything else seems to be the same as demo mode.

After a while, have to say the stompin sounds become annoying so leaving it mostly in demo mode to silence the foot buttons. Move it and it makes stompin noises. Loud.