Ask the Expert: Industrial Noise and its Mitigation

Our director of acoustics, Darren Lafon-Anthony provides information relating to industrial noise mitigation, and explains how Enzygo can provide effective solutions.

Rubbish data in, costly mitigation out…

Good mitigation advice can save thousands of pounds. However, good noise source data is critical in providing the right, effective and cost-effective solution.

The better the data, the better the advice. The poorer the data, the poorer and more costly the mitigation can be.

“It makes 65dB @ 10m!”

A recent example involved the requirement to mitigation noise from a containerised diesel generator. A request for noise emission data returned the reply of “It makes 65dB(A)@10m…”

On the surface of it this seems like a reasonable response. The containerised generator package produces a noise level of 65dB when measured at 10m from the side of the container, simple! The requirement from the local planning authority specifies that noise from the containerised generator should not exceed 60dB when measured at 10m, we need to mitigate.

Knee-jerk mitigation

Erect an acoustic barrier between the containerised generator and the receiver. Barrier installed; problem solved.

…well maybe not! Containerised generators are generally more complex than a simple box with a single noise source, they have roof mounted cooling systems and roof mounted exhaust systems which generate as much, if not more, noise than the container itself. Installation of an acoustic barrier may not provide any mitigation for roof mounted equipment.

The image above shows a typical containerised diesel generator. The whole package may give an overall noise level of 65dB(A)@10m but which element of the system contributes what level of noise to this overall figure? The container body? The exhaust outlet? The cooler fans? The intake and extract attenuators? Each element will contribute something.

Targeted mitigation

Maybe the exhaust outlet contributes more noise to the overall level than the container body. An acoustic fence, unless it is significantly high, would not provide mitigation to the exhaust outlet but would to the container body.

Steps Enzygo can take to provide the correct and most effective solution

It is imperative that noise data, including sound level and height, is supplied so that specific mitigation can be designed.

By far the best option in any mitigation strategy is early identification of noise issues and designed-in mitigation measures of individual sources. For containerised generators, and other industrial noise sources, Enzygo can provide detailed noise modelling, using our state-of-the-art software, so that the following can be considered prior to construction:

• Container lining materials
• Intake and outlet attenuator sizing
• Low noise/low speed cooling fans
• Enhanced exhaust silencers

An upgraded exhaust silencer or a low noise/low speed cooling fan can prove to be much cheaper and more effective than an expensive, partially effective, acoustic barrier.

Ensuring build quality of the container is also a must, making sure that doors are fitted correctly with adequate seals is a must as is making sure any pipework openings are properly sealed with gland plates to the inside and outside face of the container.

No such thing as too much data

There is no such thing as too much noise source data, the better and more comprehensive the data, the more accurate the noise predictions and the more effective the mitigation advice.

If you would like some advice in this regard, please do not hesitate to contact Darren Lafon-Anthony on [email protected].