Traditional and Innovative Concepts for the Noise Control of Outdoor Machines

Considerable research effort has been spent in the automotive industry to develop high qualityvehicles which combine low noise emissions with acoustically pleasant and comfortablepassenger cabins. Unfortunately, the situation for outdoor machinery is quite different, evenif effective noise and vibration control technologies are now well established. Only forequipment subject to noise limits, noise reduction has become a key issue and many studiescan be found concerning the acoustic characterization of these machines and the design ofnoise control solutions. Referring to the noise control at the operator position, the methodscurrently available for reducing the high noise levels are all based on the reduction of thesound pressure level. Consequently, even if the noise levels have been successfully reducedto comply with the current legislative requirements, these reductions are not related to a realimprovement in the operator acoustic comfort. This paper starts presenting an overview ofcurrent methodologies applied for the noise control of outdoor machines and the results ofsome relevant studies. Then it focuses on a promising hearing-related method, based on theSound Quality approach. Some studies by the author on the application of these innovativeconcepts to the noise control of compact loaders are reported. They show how this approach,including physical, psychoacoustic and psychological factors at the same time, can really establishbasic criteria for noise control able to guarantee not only reduced noise levels but alsoa reduced auditory perception of annoyance.