"Tim Snell" wrote in message
...
Evening all,

I was looking to try and reduce the intrusion of road noise into the
back
garden of my house.

snip

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.


--
Kevin Poole
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