New perspectives for the noise control of mobile machines

This paper starts presenting an overview of the noise control methodologies currently applied to mobile machines and the main results till now reached. Thanks to the EU noise limits in force for more than 30 years, many efforts have been addressed to a deeper knowledge on the main noise sources and the related noise transmission paths. As a result, the emitted sound power levels and the sound pressure level at the operator station fully meet the limits currently in force. Despite this compliance, however, the noise by these machines keeps adversely affecting both people in the surrounding areas and the operators. Some results of studies by the author aimed at overcoming this limitation are then presented. They mainly concern the tailoring of the Sound Quality approach to this specific field. The shift from criteria based on energy parameters to hearing-related criteria assures new remarkable opportunities for the noise control of these machines. Noise solutions can be found able not only to assure lower noise levels and reduced perceived annoyance, but also able to take into account the main expectations of operators referring to the noise signals as carriers of information about the state of operation of the machine.