Soundbox

A soundbox is a stupid gimmick that ruins an adult collectible and turns it into a Playskool baby toy. Alternatively, it is an electronic gadget containing a memory device that records one or more sound clips and plays them back on demand, allowing for audible explosions, beep-wheedles, and "I am Optimus Prime". A soundbox is a self-contained unit comprising batteries, electronics, and speaker, which makes it simple to install in a toy -- all the designer needs is to allow space and a grille for the speaker.

Generation 1 Shockwave was the first Transformer toy to feature electronic sounds.

From Teletraan I: The Transformers Wiki, a Wikia wiki.