If you’ve commissioned a noise impact assessment for a planning application, there’s a good chance you’ve opened the report, skimmed a few pages and quickly found yourself looking at unfamiliar graphs, decibel levels and references to British Standards.
You’re not alone.
Most people only ever read one or two acoustic reports in their lives, yet they’re expected to understand what can often be a critical piece of planning evidence. Whether you’re a homeowner, developer, architect or planning consultant, understanding what your report is actually saying will help you make better decisions and give you greater confidence throughout the planning process.
So, what should you be looking for?
Many people assume a noise impact assessment is simply there to measure how loud somewhere is. In reality, that’s only a small part of the job.
The purpose of the assessment is to answer a planning question:
The key words here are ‘acceptable impact’ which can mean different things to different people. That’s why we have standards and guidance, however by their nature as most sites are very different and noise is difficult to describe accurately, guidance tends not to be explicit and encourages judgement to be used in each situation.
Ultimately, the report is designed to help the planning authority make an informed decision.
One of the biggest misconceptions is that planning decisions are based purely on decibel levels.
They aren’t.
A measured noise level of 55 dB might be perfectly acceptable in one location but problematic in another. Context is everything.
A good acoustic consultant doesn’t simply record numbers; they interpret what those numbers mean. They consider where the noise comes from, whether it occurs during the day or at night, whether it’s continuous or intermittent, whether it contains distinctive characteristics such as tonal or impulsive sounds, and how people are likely to experience it.
This is why two sites with similar measurements can require completely different planning recommendations.
The numbers are evidence. The professional judgement is what turns that evidence into a meaningful planning assessment.
Every noise impact assessment contains technical terminology, but each metric answers a specific question.
LAeq represents the average sound energy over a period of time. It gives an overall picture of the sound levels in an environment, but it does little to describe the content of the sound in a similar way that showing how high the volume on the stereo describes the music.
LA90 is often described as the background noise level. Rather than averaging everything, it reflects the quieter underlying sound environment once short-term noise events have been filtered out. This value is accepted to be the average noise level of those occasional quiet moments in the environment. It is an important benchmark in assessing industrial or commercial noise in guidance.
LAmax measures individual maximum level of noise events. This becomes especially relevant as short duration impulse noise such as dogs barking or noise from a padel court can be particularly intrusive, without adding much to any of the other metrics we have described.
Understanding what each measurement is trying to describe is far more useful than simply knowing what the abbreviations stand for.
It can sometimes feel as though every page introduces another document with a code number.
In reality, these standards each deal with different planning questions and a good consultant can draw an inference from different sets of guidance in order to justify a judgement.
For example, BS 4142 is commonly used when assessing noise from industrial and commercial premises. BS 8233 provides guidance on achieving suitable internal and external noise conditions within buildings, while the ProPG guidance helps assess new residential developments affected by transportation noise.
An experienced consultant doesn’t simply quote these documents—they explain how they apply to your development and why particular guidance has been used.
If a report references standards without explaining their relevance, it becomes much harder for a client or planning officer to understand the reasoning behind the conclusions.
Many clients naturally turn straight to the conclusion looking for a simple yes or no answer.
Very few developments are either completely acceptable or completely unacceptable from a noise perspective and therefore the reality is usually more balanced.
Most reports will talk about acceptable levels of ‘intrusion’ of noise and justify it by referencing to benchmarks in relevant guidance.
Most assessments considers whether the identified impacts can be managed through good design or by considering mitigation and a well-written report should therefore explain not only the conclusions, but also the reasoning behind any recommended mitigation.
Planning officers read acoustic reports every week, and they quickly recognise the difference between a document that simply presents measurements and one that demonstrates genuine professional judgement.
A credible assessment should clearly explain how surveys were undertaken, why particular assessment methods were chosen, how predictions have been made and how the conclusions follow logically from the evidence.
Perhaps just as importantly, it should acknowledge uncertainty where it exists, or the reason why certain parameters have not been taken into account. Most assessments are funded by an invested party with particular interests, however a credible technical assessment process needs to be balanced.
Most importantly, the strongest reports don’t rely on technical language to sound impressive. They communicate complex issues clearly enough that planners, architects and clients can all understand the conclusions with confidence.
May Walters Acoustic Consultants (MW Acoustics) specialise in acoustics for padel and sporting facilities. In 2024 we undertook an independent programme of nearly 50 hours of measurements on padel and tennis courts to build a robust comparison dataset. The work maps how sound propagates from padel courts, characterises impact content and frequency, and highlights how patterns shift with player ability. The findings have been presented to the Institute of Acoustics (IOA) and the Chartered Institute of Environmental Health (CIEH) and inform current training content. The dataset underpins a propagation model that supports reliable predictions for planning submissions in the UK.