scribblenauts has no sound on ipad2

Had the same problem then realized mute was on in the control bar. Press home twice to bring up app switching then scroll over to the audio controls. Click the speaker button and make sure it's not muted. It's independent of the volume level so I missed it. Hope that helps.

If it is only this app that doesn't play sounds, and you're sure the mute isn't on, contact the developer.