A quick tip for turning down the volume on battery operated toys that don't have a volume control...
Sellotape! As modelled here by Vtech kitty (it has two volume settings that are both exactly the same: ear bleedingly loud).
Stick tape firmly over the speaker holes (not to be confused, like I was, with the sensor/bum holes on the cat). Leave enough holes tape-free to allow some sound out.
Disclaimer: the sellotape should be pretty hard to pick off but it's amazing what babies and toddlers can do when they put their mind to it. Also there could be a possibility that some sticky residue or discolouring could be left after removing the tape - I don't know as I only intend to remove it when hell freezes over, but I'd say don't use it on anything you want to stay pristine. In fact just pack the toy up and hide in a cupboard away from the kids or take the batteries out and say it's broken!