If Starscream is the symbol of betrayal, Soundwave is the symbol of loyalty. He rarely speaks but knows everything, and he has never tried to overthrow Megatron.
The classic image
In the 1984 cartoon Soundwave transforms into a cassette deck, and his chest holds 'cassettes' — smaller spy robots such as Laserbeak, Ravage, Rumble and Frenzy. His mechanical voice, created by Frank Welker, became one of the franchise's most recognisable.
In Prime — silence
In Transformers: Prime Soundwave almost never speaks in his own voice, only playing back recordings of others. That silence makes him eerie: he's always listening and always watching.
Why he's loyal
Different versions give different answers. The most common: Soundwave genuinely believes in Megatron's ideals and puts order above his own ambition. He is a tool that chose whom to serve. In a Decepticon army full of schemes, such an officer is priceless.
In the films
In the live-action films Soundwave is a satellite in orbit and an SUV on Earth; in Dark of the Moon he dies fighting Bumblebee.
