Glogal active control of energy density in a mock tractor cabin

Abstract

Low frequency tonal noise, associated with engine firing frequency, often makes a significant contribution to sound levels that exist inside tractor cabins. Because these tones are low frequency in nature, they present a considerable challenge to passive noise control techniques, but are good candidates for active noise control applications. The presence of such noise can also threaten machinery operators' auditory health in addition to posing a challenge to machinery manufacturers in their efforts to produce machines that meet standards for operator exposure to noise. Active minimization of acoustic energy density has been applied to a mock tractor cabin, targeting engine firing frequency in simulated static and dynamic machine conditions. Previous work has demonstrated that active control of energy density generally provides good global control of enclosed sound fields. Multiple microphones were distributed throughout the cab to verify the global nature of the control. Generated sinusoids as well as actual recorded tractor noise were used to simulate the uncontrolled acoustic field. Both static and dynamic results will be presented, showing the local attenuation at the error sensor and the global attenuation throughout the cab.