Letter to the Editor: Questions over noise mitigation solution

DEAR News Of The Area,

I WISH to draw your attention to the recently installed sound barriers on the highway bypass.

There are some concerning issues that arise from these noise walls.

It is important to understand that flat surfaces reflect sound.

This is basic physics and it means that all the large noise walls recently installed at the Coramba Rd Interchange (which have large flat surfaces on the highway side of the walls; see the June 2025 edition of the Coffs Harbour Bypass Project Update) will reflect all passing traffic noise back up the valley.

I feel for the poor people living on the west side of the highway if these walls remain as they are.

They will be significantly impacted.

There are three principles to follow when designing and building noise attenuation barriers.

That is, if they are to be effective for people living on both sides of the wall.

These are:

– High walls

– Made from dense materials.

– With irregular surfaces on the highway side of the wall. Irregular surfaces disperse noise in many directions, thereby reducing the echo effect.

Only the first two of these principles have been observed with these walls.

It is clearly understood that high smooth walls, as was standard practice up to about the 1980s, are not best practice sound mitigation.

Also many examples of best practice sound mitigation are available in other Australian states as well as internationally. Often the solution proposed is to plant in front of these walls with the aim of mitigating this sound effect.

Studies regarding this approach have in fact shown that some plantings may increase the amplification of sound.

So don’t let anyone tell you that planting will help.

Why do we, in the Coffs Harbour area, yet again, have to accept an outmoded and inferior solution to sound mitigation?

An approach that will undoubtedly make life worse for those living west of the highway.

If this approach is planned to be used elsewhere on the Bypass the social cost will spread to a whole new group of people. This is especially pertinent when the sound barriers were meant to mitigate against this social cost of the infrastructure and when a far better solution is readily at hand.

In this case a simple cost-effective solution would be to remove the panels that make up these noise walls and slot in new panels with irregular surfaces on the western face.

Alternatively, irregular shapes could be attached to the current walls for breaking up the sound.

They could also look a whole lot better, be far more attractive and a deterrent to graffiti.

Regards,
Michael SANDFORD,
Boambee.