Viscoelastic damping for noise control in an armored military vehicle

Armored military vehicles have a harsh noise environment and many times the noise levels become almost an afterthought for the vehicle designers. There are numerous noise sources such as the engine, transmission, cooling fans, and track noise. The thick armor plating and the fact that the noise sources are inside the vehicle exacerbate the noise problem. This means there are few paths for the noise to exit the vehicle into the atmosphere and the result is an extremely loud noise environment for crew and passengers. Much success has been seen in the use of active headsets for the crew, but this is not feasible for the embarked troops in an armored transport vehicle, so the noise control must be inherent to the vehicle. The development of a bulkhead panel for containing the vehicle’s engine is examined. The bulkhead panels serve the dual purpose of thermal and acoustic barriers. In addition to mass effects for reducing transmitted engine noise, viscoelastic layers are included in the panel to further passively attenuate noise transmission. The wide temperature swings seen in the panel during operation of the vehicle complicate the viscoelastic damping design. Test results from a panel prototype are presented for a testbed representing the military vehicle configuration.