Ive learned the beep speech in Animal Crossing titles is made by mashing phonemes together, creating something incoherent but likeable. Ive tried to recreate it in scratch. but due to the low speed of this code, I don't recommend it.
You can use 4 different voice fonts, from the scratch Text To Speech Tool. However, you can create you own voice fonts by replacing the TtS with your own vocal sounds.