Innovations raise bar on noise barriers

Transparent panels are one of several innovations that are changing the design of highway noise barriers.

  • Car queue in the bad traffic road. Selective focus.

The kindest way to describe most of the noise barrier walls that have been built along the edge of Ontario’s highways is “boring.” But some might call them just plain ugly and, since there are many kilometres of these barriers, that’s a whole lot of ugly.

The good news is things are changing — not all these special noise-reducing walls are dull monolithic slabs that hem in roadways, blocking the sightline of all who travel in their shadow.

Along one small stretch of the Queen Elizabeth Way in Fort Erie stands a state-of-the-art, see-through noise barrier, the first of its kind in Canada. Built into this five-metre-high wall is a portion that includes transparent acrylic panels that enable motorists to see what lies beyond — trees, sky, neighbourhoods and businesses.

Since the completion of that wall late last year, another transparent noise barrier of a different design has also been built further along the QEW in Stoney Creek.

“These walls, which incorporate transparent panels, are not only highly effective at blocking highway traffic noise, but they have the advantage of allowing light into the yards on the residential side of the barrier,” explains Doug Carter, marketing manager for Durisol Inc., the barrier manufacturer.

“From an aesthetic point of view they also make the barrier itself more interesting.”

He says that installations with larger transparent panels, such as some installed in Alaska and Europe, not only preserve scenic vistas for both motorists and nearby residents, but also enhance roadside safety by allowing for better visibility and awareness of traffic conditions.

Transparent panels are one of several innovations that are changing the design of highway noise barriers.

To be effective, barriers must be long, uninterrupted dense structures which, depending on the application, can be built from earth, wood, stucco, metal, concrete, masonry or other composite materials, including some systems that use shredded recycled tires.

Regardless of which material is used, noise levels can effectively be reduced but not eliminated. In Ontario, where noise barriers may be constructed as part of a highway expansion, new highway construction or to retrofit existing highways, the objective is to reduce noise levels to 55 decibels (see sidebar).

Sound intensity is measured on a logarithmic scale so, for example, an increase of 10 dB represents a doubling of the volume. By absorbing sound or reflecting it back, an effective noise barrier can reduce noise levels by 10 to 15 dB.

Reduction of highway noise is essential, as exposure to chronic traffic noise can affect both one’s enjoyment and health. A Cornell University study found that chronic low-level noise from everyday traffic caused increased physiological stress in children, elevating blood pressure, heart rates and stress hormones.

As well, a recent Germany study concluded that noisy environments may raise the risk of heart attack, finding that urban middle-aged adults who live near high-traffic roads were 46 per cent more likely to suffer a heart attack than those who lived in quieter neighbourhoods

While the primary goal of highway barriers is noise reduction, ideally the walls should also be visually appealing. Unfortunately many are not — a quick glance at some older barriers reveals boring, unkempt monochromatic walls littered with debris, graffiti and overgrown weeds.

Such sites can become a detriment to a city, casting it in an uninviting light with passing motorists disinclined to stop.

Neighbourhoods may be quieter by half, but are left living in the shadow of a barrier with restricted views and airflow, feeling confined with limited sunlight and deep shadowing — all serious issues that can lead to decreased property values. Businesses also suffer by no longer being in the sightline of passing customers.

Modifications to noise barriers have solved some of these issues, though often at an additional cost.

While transparent panels reduce the visible impact of the wall and allow unhindered views, other systems incorporate colour and texture, plus architectural and artistic design elements, making them more visually appealing without diminishing the acoustical effectiveness.

Some municipalities have opted to add designs that complement or reflect some aspect of the city. Barrier wall panels in Arizona have sculpted desert motifs that complement the adjoining specially landscaped areas. And stacks of giant precast books add a whimsical note to several sections of a noise barrier along a motorway in Angouleme, France.

Even a simple wave of colour can add interest to an otherwise hypnotic length of wall.

Many European countries, including Switzerland, Germany and the Netherlands, have taken advantage of the long expanse of uninterrupted noise attenuation walls by adding or incorporating solar panels or photovoltaic modules into the design.

These multipurpose barriers perform the dual task of gathering energy while also effectively reducing traffic noise, though admittedly not always in most visually appealing manner.

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