Large vehicles, such as SUVs and minivans, exhibit body boom phenomena during multiple source excitation events including rough road/impact and power-train induced events. The main cause of the boom is the low-frequency acoustic/vibroacoustic modes of the cavity being excited vi a the high acoustic transfer functions at multiple paths, due to an inherently weak body structure and/or existence of popular features such as tailgates with their corresponding dynamics. Abating the boom noise by modifying the response is the more viable and less costly option than body changes. Active acoustic damping can do such modification, cost-effectively.
A number of active, feedback controlled, boom noise damping techniques have been developed at the University of Dayton. These patented schemes [1] that rely on a speaker, a low-cost microphone and/or an accelerometer, and an electronic circuit (or a micro-controller) add a substantial amount of damping to the first (or first few) vibroacoustic modes of an enclosure such as the cabin of a vehicle. It should be noted that measurement quality accelerometers are not necessary in this application. The low-cost, MEMS accelerometers such as the ones used in air-bag systems will perform satisfactorily. The simplicity of the active boom noise damping system lends itself to be incorporated into a vehicle's sound system.
One patented [1] and two patent-pending active boom noise damping strategies are implemented on a large sport utility vehicle to damp the boom noise caused by first cavity acoustic mode and the first two vibroacoustic modes caused by the vibration of the roof and the tailgate. The effectiveness of active acoustic damping schemes is evaluated objectively and subjectively in laboratory and road tests. The control schemes add appreciable amount of damping to the targeted modes and thus abate the boom noise caused by them.