We live to some extent in the age of data collection but, largely behind the scenes, acoustics consultants have been collecting noise data for decades.

In this article, expert acoustician Derek Nash of the Association of Noise Consultants (ANC), sets out some of the key reasons why this is done, how it is carried out, and the future benefits that emerging noise monitoring technologies could bring for society.

Monitoring for design

So why do we monitor noise? Well there are two main reasons – to facilitate design – and for compliance.

In the ideal world, before any piece of noise generating plant is installed at an industrial site, someone will have gone through an exercise to minimise the noise impact where it is needed.

In my time as an acoustics consultant, I could say that among the most contentious and difficult cases of noise nuisance to resolve have arisen where an industrial area neighbours onto a residential area and, for whatever reason, that minimisation activity has not happened.

An example of this might be where a printing factory on the edge of an industrial area has installed an amazing new suction system to rapidly clear paper waste from cutting tables within the premises.

As part of this, a very large, high-power extract fan has been placed in the factory car park and runs for 24 hours a day.

Needless to say, the residents living some 30 metres away, who are used to opening their windows at night for cooling, are not very happy.

As a result, the factory owners now have to deal with the fallout when their local authority deems the factory to be generating a statutory noise nuisance, and places a noise abatement notice on them.

Another example might be where an industrial laundrette – again located on the edge of a very large industrial area adjacent to residences – has undertaken some serious upgrades of their dryers.

The scenario continues that this has also resulted in a noise abatement notice being served. We can be pretty certain that, if this occurs at this point in the process, the costs incurred from downtime and retrospectively designing and fitting noise mitigation measures will usually become eye watering.

In both these scenarios, the pain that is caused to the factory operators – and not least the residents that have suddenly found themselves no longer able to sleep – could have been avoided if the plant schemes had been designed to minimise this noise risk from the outset.

Minimising impact

So how do you design plant to minimise the risk of creating a significant noise impact on residents you may ask?

Well this is where the noise monitoring comes in.

While some countries do, in the UK, we don’t have fixed limits for allowable noise from industrial sites at their boundaries.

The approach we take is to set limits for each location, which are appropriate to the current noise climate.

Due to this approach, the first part of any exercise to control the noise from industrial or building services plant is to carry out a noise monitoring exercise.

The purpose of this exercise is to come up with typical background noise levels for areas that may be sensitive to the noise you will potentially create.

The advantage of this approach is that areas which currently have low noise levels keep them, whereas the burden to mitigate noise levels in areas with a higher noise climate – if they are located near a busy road for example – is reduced.

Once you have a profile for the existing noise climate, you can then make sure the impact of the plant you want to install is minimised, and it is the noise monitoring that facilitates this.

I think it’s also worth saying that the earlier this exercise is undertaken in the design process, the greater the benefits in terms of time and cost.

It is considerably easier to say “could we move the generator here” to take advantage of the natural acoustic screening provided by the building; for example, when looking at a piece of paper around a table; than once the machinery is up and running. Worse still would be having no choice but to construct a costly acoustic enclosure around the generator if the situation was that it cannot be moved.

Furthermore, once residents have tuned into a noise source to the extent that they have complained to the local authority about it, it is very difficult for them to tune back out.

This means the job of suitably mitigating noise levels has become significantly harder than it would have been if it had never arisen at all.

Monitoring for compliance

We now move onto the second reason for monitoring – compliance.

We have probably all heard the expression “what gets measured gets done.” Well this couldn’t be truer than in the case of noise monitoring for compliance.

The harsh realisation that the number prescribed to the noise generated by your building site is higher than it should be, and you’ve broken the law can really focus the mind on noise control.

It is no secret that requests by local planning authorities for continuous noise monitoring during demolition and construction are becoming more and more prevalent.

The same may well be true for large industrial sites, and I suspect that, if not now, it will become the case in the near future.

The reason for the noise monitoring request is clearly to protect noise sensitivities within the vicinity of the site.

However, thinking of it as purely a compliance exercise is also to miss a valuable opportunity.

The data is valuable

Consider the construction industry. Although acousticians can model noise generated by plant and construction activities to some extent, there is no substitute for actual site data.

This is because models include a large number of assumptions, such as what plant will be used, where it will be, for how long it will be there, and for how long it will operate.

Justifiably, worst case assumptions are normally made, as planning for this eventuality means all potential scenarios should be addressed.

Although this is a safe approach, it can lead to over-specification of mitigation measures, such as opting for more costly and time-consuming techniques where quicker, cheaper methods may be just as suitable.

Furthermore, if data is obtained from several jobs showing the actual noise levels, this can serve as valuable evidence to inform future decisions on plant selections, demolition techniques, piling techniques and other factors, rather than using a worst-case model in isolation.

In fact, every time a site is monitored, a valuable data asset is being built, which should be used to gain an advantage.

“one of the potential benefits for the noise monitoring industry from the push in smartphone technology is the availability of cheap, small, low-powered, high-sensitivity and high-accuracy microphones”

With some smart interrogation, it can be established how the noise levels compare in certain situations, for example by using nibblers versus breakers, the actual cost-benefit of using vibratory pile drivers versus impact drivers, and whether there is a need for increased or a case for reduced monitoring.

Having this type of data can be invaluable when making decisions about future projects. It can also provide a great way to demonstrate to the various authorities a responsible attitude of using monitoring to minimise future risks.

In fact, given the significant benefits it brings, we would strongly advocate undertaking monitoring as a matter of course where possible.

In the case of an industrial site, closer investigation shows the benefits are just as readily available.

“to make informed decisions on the basis of noise monitoring, the data needs to be available as it happens”

By knowing how much noise is generated by the plant operating on a site under various operational conditions, it is possible to identify when and for how long different processes can operate before the risk is run of causing a nuisance.

In addition, if plant hasn’t changed but noise levels have, it could be a useful indicator that the equipment is not operating as efficiently as it once did.

Real-time data is key

To make informed decisions on the basis of noise monitoring, the data needs to be available as it happens.

Fortunately, we live in a time where everything is getting ‘smarter’, so access to noise levels can be as simple as pulling out your smartphone and opening a webpage.

It is very important that the system delivers the information in a form that makes sense.

Acousticians use a variety of metrics that utilise some pretty difficult maths.

Fortunately, smart systems these days will give a traffic-light system method of feedback, which gives an alert if something needs to be done.

In addition, these will explain not just what the levels are, but how the figures compare to five minutes ago, an hour ago, yesterday, and other timed points required.

That way if an activity does generate noise, it can be spotted immediately and, if it is at a level of concern, action can be taken.

Looking to the future

One of the potential benefits for the noise monitoring industry from the push in smartphone technology is the availability of cheap, small, lowpowered, high-sensitivity and high-accuracy microphones.

Traditionally, microphones which can provide the level of accuracy needed for noise monitoring (where the data may need to be used as evidence in court, for example) have cost hundreds to thousands of pounds, have been very sensitive to the environment (i.e. with regards to temperature, humidity etc.), and have needed regular on-site calibration to demonstrate continued accuracy.

The result of this is that the costs for noise monitoring have always been high, and prohibitive to large-scale exercises.

However, new microphone technology has the potential to change all this. It is now feasible that the hardware required to accurately measure noise levels, and process these in a way akin to a modern sound level meter could fit on a circuit board not much bigger than a postage stamp.

This brings the feasibility for common-place, city-wide smart noise monitoring much more within reach.

“it is now feasible that the hardware required to accurately measure noise levels, could fit on a circuit board not much bigger than a postage stamp”

The benefits this would bring are substantial. Going back to the adage that what gets measured gets done, in a rapidly changing society unless levels are monitored, who is to say what the actual impact of an increase in drones, other air-traffic, or increasing population has been? Or the benefits of the reduction in noise levels from electric vehicles?

Further to this, imagine being able to determine in real-time which routes and how fast transportation sources should move around cities to ensure sensitive areas, such as schools, hospitals and residences for example, are not exposed to higher daily noise levels than they should be. Or knowing to the minute when a specific construction site should down tools for the day to avoid creating a significant adverse impact.

The link between higher noise level exposure and conditions like hypertension has been established for some time, but large-scale noise monitoring is needed to facilitate action.

To conclude, I predict that this is the future for noise monitoring. Given how significant our noise climate is on our wellbeing, the changes in society that new technologies could facilitate make the future sound pretty good.