In message , The Natural
Philosopher writes

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

Yes that is my understanding

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.,

Ah! Bunds.

My wife wants one.

Line of sight to our village by-pass is 100m. Pause for gasps of envy at
such solitude.... However, this is a river valley and the highway
remains elevated for around 0.5k. We have the shelter belt of Leylandi
but road noise remains intrusive (best at rush hour when they are
queuing). I looked at sound reduction fencing, the stretch on the M1
near South Luton cost around 6million, and would need to be at road
level; some 20' up.

A bund would appear to be the ideal solution. Excellent noise reduction,
cheap; can use class A waste and charge by the ton for tipping. We
already own the land so kindly work out how many tons of fill would be
needed for something 30' high and around 1000'long:-)

There is the slight problem that we are upstream and the bund would dam
the river.

regards
--
Tim Lamb