Dawn's a smart mom:
I don't know about you, but I've found that most children's toys that 'talk' are way too loud - - too loud for me, and I'm sure for the tiny little ears that are even closer to the toy. So, I finally figured out a way to quiet them.
All the advice about covering with tape and stickers didn't work for my little J, since she's fascinated by anything sticky and immediately sets out on a mission to peel it off. One day, while working around the house, I realized the caulk I was using could be a lifesaver. Test toy number one was a Dora plastic bike that was frighteningly loud. I carefully caulked the speaker holes and......Voila! MUCH quieter. (See attached photo) You can still hear the music and what she's saying clearly (well, as clearly as before), the volume's just much lower. I've found that it works for all plastic toys.
For tiny, tiny speaker holes, I squirt a little pile of caulk on wax paper and apply it to the speaker with a q-tip, toothpick or handle end of a small paintbrush. Ahhhhh, the peace and quiet.
Related: Muffling noisy toys