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N oise Reduction
In an untreated production hall there was a large machine generating a sound level of 85 dB(A) at the workstation. In addition, there also were 20 machines individually generating a sound level of 72 dB(A) at the same location.
When planning an improvement of work conditions, the management was quick to point out that a serious noise reduction effort was needed on the large machine. An expensive enclosure was custom built by a contractor with a planned noise reduction of 20 dB(A). On commissioning, it was discovered that the sound level at the workstation was still 85 dB(A) due to the noise contribution from the smaller machines.
Lesson Learned: Do take all the noise contributions into account, as numerous low-level noise sources may add up to represent a significant contributor.
It Would Have Been So Simple
When a highly sophisticated maintenance center was designed, the end user called for a suitably bright architect and his usual structural engineer to draft the relevant drawings. While everybody’s attention was focused on a huge facility of this center, nobody paid any attention to smaller spaces that would eventually be easy to care for should the need arise.
It turned out that absorptive treatment really was needed in those small spaces; unfortunately, a mobile crane had been installed under the upper slab and there was not enough clearance left to apply the usual cheap absorptive baffles. This eventually led to some expensive corrective work involving the fixation of absorptive materials under the upper slab.
Lesson Learned: Noise control measures are costly when done afterwards!
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