Energy Density Active Noise Control in an Earthmoving Machine Cab

Conventional active noise control (ANC) systems attempt to minimize pressure at an error sensor (or sensors) to achieve control, and often result in a relatively small zone of control. Considering a practical application in a vehicle, this approach is acceptable provided the operator’s head remains within the control zone. In the case of an earthmoving machine, an operator’s head regularly moves about the cab, either because of the motion of the machine during operation or as the operator moves about to perform various tasks. By minimizing Energy Density (ED), instead of pressure, a potentially larger control zone may be achieved. Active control of the sound field within an earthmoving machine cab was attempted using the ED technique. The scope was limited to controlling the engine firing frequency tonal within the cab with the machine running, but in a static condition (engine idle). Frequency response and spatial results show the method achieved nearly global control within the cab and effectively reduced the Aweighted sound pressure level by a few decibels, despite only reducing a single low frequency tone. In this sense, active control using ED has the potential to be more suitable to earthmoving machine applications than pressure techniques.