The sound of silence

Studies into acoustics often focus on improving sound quality, volume or clarity. But what about using sound to imperceptibly improve an environment? Anna Mitchell explores psychoacoustics and environmental health with psychology professor, Mats Nilsson.

“Parks are the lungs of a city,” said Frederick Law Olmsted, American journalist and landscape designer who co-developed New York’s Central Park. The comment does much to convey the sense of calm, relaxation and regeneration that a green space can provide in the centre of a built-up urban environment. But how do you stop the urban sprawl infiltrating, contaminating and polluting these special places? In particular how do you handle the noise that leaks from nearby roads and urban spaces?

It’s an interesting acoustic challenge and one that has been tackled head on by a research team working at Mariatorget, a central square in Stockholm Sweden. The installation combines acoustic design and sound art research in an attempt to tackle an area that suffers acutely with noise pollution. A team, boasting expertise in acoustic simulation and psychoacoustics, is conducting the research funded by the Swedish Research Council. APart and Sennheiser Nordic, the manufacturer’s local distributor, sponsored the project with free amps and speakers.

The project brought together academics from numerous Stockholm institutes: Björn Hellström, from the College of Arts, Crafts and Design; Mats Nilsson, from the Department of Psychology at Stockholm University and Peter Becker and Peter Lundén at the Interactive Institute.

The research question to be tackled was “How to develop and apply acoustic artefacts and design methodologies for improving soundscapes in outdoor spaces?” The research encompassed city parks and city squares and two types of acoustic design artefacts.

Firstly the team investigated “Dynamic promotion of qualitative site specific sounds”. These include exploring the overall site specific sonic atmosphere, sounds for activities, birds and fountains, in a bid to create an improved environment. And, secondly; “sound-art installations” which are designed to create delimited auditory sub-spaces within the park or square.

Stockholm University’s Mats Nilsson is also affiliated with environmental health institutions and specialises in perception psychology. He has a strong background in psychoacoustics and researches the perception of environmental sound, measuring and analysing acoustics in various spaces. He also works in noise and health research, exploring the noise exposure people experience and its resulting health outcomes.

Nilsson says he was interested in music from an early age and during the course of his studies found it quite natural to move into acoustics and psychology. An early thesis on psychoacoustics served to further spark his interest and he embarked on a PhD that took him further into the topic at Stockholm University.

At the Mariatorget project Nilsson is largely involved with sound field and sonic recordings that are used for perception and listening experiments. “I’m working closely with Peter Lundén, a computer programmer and audio expert at the Interactive Institute,” says Nilsson. “He has simulated the sound environment at Mariatorget and we are working with the findings together now.

“There are several applications for this project,” continues Nilsson. “Exploring these noise and health issues we can quantify the risk of noise exposure on people’s dwellings and we can motivate or argue for noise reduction on a political level which may, in the end, lead to a more healthy sound environment.

“Specifically looking at the Mariatorget project we are studying the quality of sound environments in recreational areas or city parks. These areas are much more difficult to characterise acoustically. Their decibel levels do not tell us very much about the quality of the sound environment because whilst it shows us the extent of the noise it does not account for the presence of other pleasant sounds.

Nilsson explains that the project at Mariatorget aims to develop a methodology for a proof that will enable city planners to improve sound quality in city parks. Furthermore, the team aims to find acoustic indicators that can be applied to spaces and the outcome of the findings used to improve quality.

Finally Nilsson has one final specific aim with regards to auralisation. “The goal is to simulate sound environments before they are built, we want to let people listen to how a space will sound before it is created. It will be a tool for city planners and using it they can listen to various different solutions. So, for example, maybe instead of building the barriers they realise it would be better to slow down the speed of traffic or find some other solution completely. This is a cost efficient way of creating high quality environments.”

Specifically the team is working on a tool to demonstrate the benefits a product of this kind could provide. “It’s a demonstrator project called Listen,” explains Nilsson adding that it will be a long time before the tool is ready for commercial use. “The first demonstrator will be ready by September next year. We have to first demonstrate the possibilities of this technology then it’s a long time to prototype and even longer for a product of course. It takes time.”

However, the project at Mariatorget isn’t just trying to resolve issues with intrusive sound or even trying to determine and anticipate how sound will affect an area. The project includes a work centred on making the environment a more pleasant place by “creating a fictional soundscape”. This particular side of the project was very much handled by Hellström. In Mariatorget he installed a sound system with a big amplifier and outdoor speakers to allow him to pipe in nature sounds, such as bird song or waterfall noise, around the square.

Nilsson says that deciding whether or not to add sound to public places is a widely debated question. “That’s a controversial issue and I would say I myself am a little undecided on that point. I see good things and bad things but that’s not really part of my work to look into that. Adding sound is one thing but adding loudspeakers is another and I have noticed that some people react to this negatively. It’s a controversial issue and I’m not really sure it will work. If you do go down that route you have to be very careful.”

He does however point out that the method can work in certain situations but an installation has to be handled very carefully. “You have to be very good at what you are doing and very competent,” he explains. “Björn has been working on this for a long time and he knows what works. I think if [city planners] started to set up loudspeakers in parks it could be disastrous so I believe you have to be very careful.

“Björn made the sound installation as part of his project. The idea was to evaluate limitations as part of our research. His work is interesting but it’s still at the emulation stage. Of course the speakers are there and you can listen to them but now we are seeing if people react positively to them.”

Nilsson stresses that in order for any installation of this kind to work it’s vital that the resulting solution reduces negative sounds and doesn’t just add other sounds to the cacophony created by road and rail traffic. “It’s only when you have no choice that you might try to fight negative noise WITH positive sounds,” he says.

It’s amazing to learn how sound can actually make a difference to people’s lives and the environment they reside and work in. If the project is a success then the model could be rolled out throughout the world’s cities and will hopefully be coming soon to a park near you.

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