While Soundwave is a prominent character in the Transformers universe, he isn't playable in this particular game. The DS version features a different roster of characters than the console versions.
However, you can play as other iconic Decepticons such as:
* Megatron: The leader of the Decepticons.
* Starscream: Megatron's second-in-command, always scheming for power.
* Shockwave: A brilliant but ruthless scientist.
Remember, the DS version is a simplified version of the game compared to the console releases, so you won't encounter all the characters you might expect.