The Thermal on our 99 BASE is about 6dB louder in the cabin than stock. Keep in mind that it is designed to have a sound of its own. The "drone/rumble" under the car becomes pleasing as it breaks in. Took about 1500 miles to fully bed it in. We travel for hours at a time with the stereo only a few clicks higher than without the Thermal and NO problems talking, listening or driving along. If the engine is run wide open it does NOT sound like certain other exhausts (ie 'fart can'). From the standpoint of police - no problem at all.