Oh Flounder! The words other pets use to communicate with you aren't in sounds, because you don't have any ears to hear sounds with (hehehe)!!!
Other pets can communicate with you by writing text messages to you in 1 of 3 possible places:
1. Underneath this picture in the "comments" section
2. At the bottom of this page underneath your Pet Family in the 2nd "comments" section
3. In the "message" box available when they send you a gift that appears in your "gifts received" or "app gifts" on your wish list