A vehicle's sound is primarily impacted by the engine and exhaust systems installed. Larger volume engines produce more exhaust, which typically deepens the sound and increases the audible volume. Exhaust systems may be installed which allow the sound presence of the exhaust system to be dampened, amplified, made raspy or throaty or mellowed. With a given engine, the style of exhaust and specific components used may be altered to change the sound presence.
Install a different muffler. The muffler is the single largest contributor to the sound of the exhaust. Mufflers which allow virtually all the exhaust gases to be ported straight through with very little obstruction or dampening will produce some of the most audible exhaust presence. Multiple chambered mufflers will allow the exhaust gases to be dampened within the chambers and to allow some of the resonance to smooth or mellow the sound produced (because each cylinder fires separately, the sounds produced by the porting of exhaust from each cylinder can be used to balance or partially cancel the sound produced by another cylinder). Longer and larger exhausts will usually mellow and deepen the sound the system produces. Mufflers that force the exhaust gases through sound dampening chambers or restrict the gases will reduce the sound produced (restriction forces the sound waves to bounce against each other and reduces audible output) . Mufflers with linings that specifically absorb sound waves will also dampen the sound output.
Install a resonator. When installed, a resonator allows more of the sound waves to acoustically rebound within the resonator's chamber. This allows the sound waves to bounce off the walls of the chamber and cancel other sound waves in the resonator. The result is a dampening effect of the exhaust presence. If the resonator is used in place of a catalytic converter, the sound presence may increase. Because the catalytic converter acts as a dampening of the exhaust sound, removing the catalytic converter and replacing it with a resonator may result in a net increase in the sound volume. Check the legality before removing a catalytic converter.
Install a "straight through" exhaust system. Exhaust chambers and pipes that allow gases to pass directly from the engine (or catalytic converter) to the exhaust tail without obstruction are considered to be straight through designs. Straight through designs minimise the obstruction to sound waves and result in an exhaust that is typically louder and responds directly to engine RPMs (noted as a throaty sound, growl, or barking sound as a result of the exhaust gases produced by each cylinder arriving at the tailpipe virtually unobstructed).
Install an aftermarket tip. Dual-walled, bevelled and flared tips generally amplify the sound produced by the exhaust. Exhaust tips with outlets larger than the exhaust pipe inlet may amplify sound. Resonated exhaust tips are lined with fibreglass or sound dampening material and are specifically designed to reduce the sound output of the exhaust system.
Install a cross-pipe. If you have a dual exhaust system and both exhausts do not intermingle gases, you can significantly alter the sound by installing a cross-pipe. The pipe allows gases from one exhaust system to intermingle with exhaust gases from the other system. Because exhaust gas porting occurs at intermittent rates, the mingling of gases will smooth the total flow and mellow the total sound. Cross-pipe, x-pipe, h-pipe, y-pipe designs and dual-in muffler designs all use the intermingling of gases to balance the exhaust output.
Wrap the muffler and exhaust with an acoustic wrap (or spray with a sound dampening high temperature material). Acoustic wraps and sound dampening sprays designed for use on an exhaust system may reduce transferred vibrations and alter the total sound of the exhaust system.
Removal of the catalytic converter alters the emissions output of the vehicle. Before removing the removing a catalytic converter, understand the laws and requirements for your vehicle by contacting your state's Department of Motor Vehicles (DMV) or similar agency.