Autolycus wrote:


"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.

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?).

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.

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

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

Yes that is my understanding