Sound is an important element of our environment irrespective of whether we want to maximise it or reduce it. Here we speak to acoustics experts about the impact of noise on people, and how it’s managed through good design.

Noise, defined as ‘unwanted sound’ is one of the top environmental hazards. The World Health Organisation says environmental noise exposure is responsible for a range of health effects including annoyance, sleep disturbance, stress-related mental health risks, and in high-noise environments, tinnitus.

Kezia Lloyd says that workplaces which have embraced open-plan environments to encourage innovation, creativity and collaboration, often find that they create unexpected noise challenges that result in annoyance and stress.

“In an open plan office you don’t want to be able to hear the person on the phone next to you because it can distract you from what you need to concentrate on. If you can clearly understand words spoken in a conversation that you’re not part of – that’s distracting and annoying noise. Obviously for the person that’s trying to listen to that conversation, that’s great, but for others it’s unwanted.”

One way this can be combatted is by increasing the background noise level to mask conversation, so that the content is not clear to the unintended listener.

“A good place to see this in action is a GPs office, where you’ve often got terrible walls and doors, so they add piped music – that’s to mask the sound of highly confidential conversations and make people feel more at ease. Current technologies allow you to subtlety add noise to a space and adapt that spectrum in an active way. The system can hear the sound that’s going on in a space and then change the spectrum to balance it out. It’s not new technology but it’s smarter than it’s ever been before.”

Thanks to the emerging field of psychoacoustics, there is more awareness about the auditory spectrum and how different people respond to sound.

“We know that some people will thrive in a busy, buzzy environment and be able to get a heap done, but others require a quiet, serene environment. That’s why there’s a big shift to modern working and learning environments with spaces that cater to a range of needs. We know that you need to give people options because no one is the same.”

Kezia emphasises that ultimately, judging whether there is too much noise is a matter of personal preference and the environment.

Richard Jackett is one of the foremost experts on the impact unwanted road noise has on people and communities – he’s spent most of his career assessing it.

“Fundamentally it comes down to how acceptable noise is. WSP has done much of the research that underpins road noise guidance and standards in New Zealand. What was deemed reasonable for New Zealand road traffic is 57 decibels.”

However, Richard points out that New Zealand’s standardised algorithms for predicting traffic noise were last reviewed 30 years ago, highlighting there is room for improvement.

“The model has done a good job, but it was developed at a time when the top selling cars were the VN Commodore and EA Falcon. Things have changed dramatically since then and we need to consider a broader range of scenarios, such as intersection and night time noise.”

It takes time to respond to such changes due to the requirement for robust evidence of the problem. Because noise assessments are often brought before council chambers or the Environment Court, updating regulation is a significant undertaking. New limits and models will also change how large projects are designed and how planners tackle residential developments.

Interestingly, Richard says the expectation that road noise will be drastically reduced with the shift towards electric vehicles is incorrect.

“It’s the interaction between the tyre and the road that generates most of the noise – certainly for cars – so quieter engines and no exhaust won’t make an urban environment that much quieter. The big shift will come when we see more electric buses and trucks.”

Richard’s team helps with planning decisions, investigates noise complaints and recommends solutions.

“We try to get in as early as possible in the decision making to ensure the road alignment has the least amount of impact – that’s the best thing we can do for people. The next thing is to find the road surface that generates the least amount of noise.”

Ideally road noise should be limited at source, he says, rather than relying on expensive interventions such as noise walls, which cause shading, or the installation of double-glazing on houses.

“To be honest, we get limited traction on where the road goes because there is so much involved in making those decisions, but we can influence the road surface. Greater investment on the surface means less spend on mitigating with barriers, and house treatments, so it’s a pretty compelling case.”

This approach has been successfully applied to large projects including the Waikato Expressway and Southern Links.

Richard has seen first-hand the impact noise has on people, and says that even small changes have a tangible effect on the people who have to live with it.

“I was involved in a research project that went into people’s houses and talked to them about a recent change in their noise exposure. They talked about sleeping with windows closed, spending more time in the kitchen because it was easier to talk there, listening to the TV with the volume on level 20 rather than 15.”

There’s always a balance he says, the trick is in finding a solution that satisfies both sides and being able to justify it with evidence.

Kezia Lloyd is Head of Specialist Services at WSP, incorporating Acoustics, Fire, Façades, and Sustainability disciplines. As a Chartered Acoustic Engineer, she draws on her experience to develop innovative acoustics solutions for clients across multiple sectors.

Richard Jackett is Principal Engineering Scientist – Acoustics at WSP. His work focuses on defining and performing applied environmental research and consultation projects, as well as proving guidance for acoustics, quantitative analysis, and modelling.