This new customer came in because he was hearing a weird noise by his subwoofer box every time the bass hit. After we listened to it we determined that the box was vibrating against the back wall of his truck. We introduced him to the sound deadening material Hushmat. We installed it for him through out the back wall. When we put the box back it the weird noise was gone and the overall sound of the bass was clearer without the added vibration. This Hushmat installation was recommended and installed by the tech crew at Audio Express 2003 Arden Way, Sacramento, California 95825 (916) 920-4262 your car audio custom installation experts.