A health care company manufacturing medical containers used a process of multi-stage forming on high-speed, automatic, coil-feed transfer presses. The presses consisted of a number of cam-driven, mechanical hammers mounted on heavy steel base frames, factory fitted with enclosures acting both as a safety guard and to reduce some noise emission.
It was impossible to change the noise generating mechanism of the press, nor would increasing the acoustic absorption have resulted in sufficient noise reduction. In addition, the shop ran on 24-hour shifts, preventing any prolonged acoustic examination of a given press running in isolation.
A sound intensity survey of each press was carried out, enabling the acoustic energy output of any selected part of the machine to be measured in isolation.
The survey identified those presses that were the major contributors to overall shop noise and how that output was distributed over the various panels of the machine. The noise sources and resulting treatment were as follows:
About £2000 per press. (1995)
A noise reduction of up to 11 dB per press.
Photographs courtesy of 3M Neotechnic Limited. Noise control survey conducted by Ian Sharland Limited.