Reducing road noise in garden with acoustic reflective barriers

[Tim Snell]

Evening all,

I was looking to try and reduce the intrusion of road noise into the back garden of my house. There is a 40mph B road directly behind the garden and it can sometimes get quite busy. The noise is not a major issue in the house (22m away) but it can make the garden feel less than peaceful.

I have seen a number of 'noise barriers' advertised from companies e.g.

are basically motorway noise barriers as far as I can see

I am contemplating either buying this as a kit and DIYing the install, trying to make similar or just getting it fitted.

However it is quite pricey (think £100/m fitted) and I wanted to know if anyone has opinions as to how effective it might be OR better still experience of such a barrier.

Some facts The road is about 2m from the fence at the back of the property. AT present there is an exisitng old 6ft feather baor fence at the back of the garden. One side has chainlink fence and leylandi - this is then open to the road and the other just leylandi - this is between adjacent gardens. Where there is chainlink and leylandi you really hear the road!!!

I was thinking about going up to 2.4m (with planning perm.) at rear of garden and 2m at sides.

I would be really interested to hear any constructive comments, and how other people had tried to reduce noise in their gardens

Thanks Tim

[Colin Wilson]

Not tried it myself, but there are several manufacturers of "acoustic fencing" if you throw that term into google...

This one also gives an idea about the level of reduction you might get from their stuff...

or

[Clive Mitchell]

In message , Tim Snell writes

Wouldn't a wall of conifers have an effect on absorbing the noise?

[Tim Snell]

Apparently you need a huge amount of vegetation (50m) to halve the noise... However foliage does give the all important psychological barrier that prevents viewing the road.

Think fence + trellis + attractive climbers - leylandi :)

[Clive Mitchell]

In message , Tim Snell writes

What if they were planted in the middle of the road. That would stop all the traffic then there's be no noise.

On a more serious note, a water feature could help raise ambient noise levels in a pleasing manner and make the traffic noise less of a nuisance.

[David Sims]

The absolute enemy of noise reduction are gaps of any kind (hence why vegetation is so bad)

I would suggest a normal stout closeboard or lap fence with thick boards as high as you can go. Seal any and every gap

[Autolycus]

It's 30 years since I worked in the Noise Unit of a County Council, so I may be a little rusty on the subject, but iirc the two big factors were the plan angle obscured by the barrier, and the path difference between the direct line of sight from the observer to a point just (0.5m?) above the road surface and the distance from the source to the observer via the top of the barrier.

In other words, a barrier is ineffective if the noise can "get round the side", and "the higher, and closer to the road, the better". The barrier itself doesn't need to be anything too special, but must not have any holes or gaps.

As someone else mentioned, hedges, trees, and so on, have mainly a psychological effect.

This is all based on the prediction methods that were introduced in the Land Compensation Act, and relate to L10 noise levels, which were favoured at the time (the A-weighted noise level exceeded for 10% of the time). I believe that Leq is now favoured, but for some individuals it may be peak noise levels, or peaks relative to ambient levels, that matter more.

I once lived in a house where the bedroom window was level with, and about 8 yards away from, the East Coast Main Line down line. L10 would have been quite low, Leq probably reasonable, but Lpeak bloody horrendous. Fortunately, the Deltics were on the up line, about 10ft further away, when they were all opening up to full power.

[nightjar]

I would go for a brick wall. They have to be very badly made to have gaps and the mass will also help to prevent them transmitting noise.

Colin Bignell

[Tim Snell]

Yes that is a good idea, especially if it s close to seating etc.

Th

[Tim Snell]

Wow thanks. I think I understand the path difference but what is the plan angle? Is it not the angle that creates the path difference (over the distance from source to observer?).

So a heavy fence without gaps...which is basically what those noise barriers are. They seem to employ cover boards or tongue/groove to avoid the normal endemic gaps you get with fencing

Yes that is my understanding

[Autolycus]

Draw a plan of the road, the barrier, and the point in the garden you're thinking about. If the road were infinitely long and straight, and there were no barrier, it would subtend an angle of 180 degrees. Now think of the barrier blocking part of the view of the road. This reduces the 180 degree "view", depending on the site geometry, such as the curvature of the road and the length of the barrier. To maximise the angle obscured, the barrier may need to extend onto your neighbour's land, or return at a right angle along the boundary. Other houses, etc, may help to reduce the angle of view, but if the road rises, it may become visible over the barrier.

[Tim Snell]

Yes but how much would that cost??

Seriously 2.4m/8ft high by 25m what on earth would that cost...does anyone know?

[Owain]

If there's enough space, and access for a tipper lorry, an earth embankment may be very effective, and comparatively cheap.

Owain

[nightjar]

I would expect it to be cheaper than a specialised noise reflecting fence, especially if you use high density concrete block, rather than brick.

This being uk.d-i-y you would, of course do your own bricklaying and a wall that big would give you a fair bit of practice. :-)

Colin Bignell

[Dave]

You have no concept of the noise that comes from a road.

I live in an area that has an old motorway to our left (the first in England) a slightly newer one that joins up to it, at our right and an almost brand spanking new one that crosses the pair of them.

Old one is only audible on the quietest summer night. The next newer one is audible on any quiet night and even during a quiet day and the new boy on the block makes our back garden unavailable outside the hours of

0700 hrs to about 2200 hrs for a conversation above about 10 to 15 foot.

I complained to our MP about the noise and suggested that the use of quiet tarmac would reduce the noise by several decibels. He passed this on to the relevant authority, who wrote back and said that as the surface of the road was good, any resurfacing was not on the immediate agenda and that I had several tall trees between me and the motorway closest to us to prevent any noise from disturbing us.

I don't know where these trees are, but I can see the bridge that the motorway takes over a feeder road to it and all it has is a plastic panel on it. Estimated height about 6 foot.

So why can I hear all three motorways day and night?

Dave

[The Natural Philosopher]

Leylandii good, brick wall better.

[The Natural Philosopher]

Diffraction.

My mothers house was - when I were a nipper - a reasonably quiet place. Ok the electric trains a mile away were audible. And I got used to the Heathrow holding pattern and the V bombers landing at the unmarked airfield just down the road.

Then they built the M25. Its about 5 miles away, and it roars day and night, and you could hear it all the time.

Another reaoson to no longer live in Surrey.

[The Natural Philosopher]

Probably a grand or so off the top of my head.

Less than a pair of double glazed windows

[The Natural Philosopher]

Not so,. Trees are actually pretty good if you have enough of them. Leylanddi especially. The darker it is under the tree the more of everything gets absorbed.

However yuu can't beat concrete blocks..faced with brick on the 'fair side' for aesthetics..oh except an earth bank.

There is a place at thelocal service airfield where they run up engines..jets and turboprops...there is a huge bank. Its quieter behind that bank than it is half a mile across the airfield to the nearest other boundary.,

[Thomas Prufer]

Another idea, site in German, as an idea:

they've patented an idea where two willow fences are tied together and the space between is filled with earth. The willows sprout and grow, solidifying everything, giving a solid and growing wall.

(Needs plenty of water, I expect, and a gardener, else the willows might get out of hand.)

Thomas Prufer