2 of my friends have gone through this process. They put on their silencers just to make sure and they both passed the test. They took the signed off ticket to court and paid $10. Now, here's the good part, whenever they get pulled over for the exhaust, they show the ticket they received previuosly as being approved for complying with the CA DB limit and have not been cited since(and they've been pulled over at least 2 times since).

The phone number to schedule a DB test when you get a ticket for exhaust, in CA, is:
(800)622-7733