Sonic is the fastest thing alive and a top grade hero in his world. He is seen as an optimist and suspicious of Shadow from the start. Sonic's caring nature tends to be seen as sometimes overprotective when it comes to his friends. But none the less he's cheery unless in a tight squeeze.

I imagine his voice to be light but a little low, we all know how his voice can be, you don't have to be as similar as the voice reference 

Voice Reference: https://www.youtube.com/watch?v=7nQG8cs0K7o