The hydraulic power pack driving a baler was the cause of both occupational noise issues on-site and noise complaints off-site. Whilst the former was simply a case of the overall noise level at 87dB(A) requiring the use of hearing protection, the latter was a result of the highly tonal - and therefore annoying - nature of the noise. We designed engineering noise control modifications that not only cut the overall noise level to 76dB(A) at 1m (no PPE required), but also eliminated the tonal noise issue.
The noise sources were ranked and modified as follows:-
Care was taken to ensure that there were no vibration isolation short circuits.
These modifications cut the overall noise from the power pack by 9dB(A). In addition, care had been taken to address the off-site tonal noise problem. The major problem tones were reduced by up to 17dB (98%) as shown by this narrow band frequency analysis.
The engineering modifications were low-cost, easy to install using a local contractor and had no effect on normal operation, access or maintenance.