Scattered across the landscape of north west Europe are prehistoric monuments from the Neolithic era. Stone circles like Stonehenge as well as covered burial chambers can be over 5,000 years old.

The stones stand silent in the landscape but a new study of these ancient structures has found that they possess some remarkable acoustical properties.

When Aaron Watson of Reading University visited a Neolithic stone circle in Scotland he noticed a curious echo which changed as he moved around inside the circle.

Tests with audio recording equipment showed that the large, flat-sided stones were positioned in such a way to reflect sound towards the centre of the stone circle.

The cramped entrance to a Neolithic burial mound

But it is the Neolithic burial mounds that have the strangest properties. They usually consist of a long chamber which is reached by crawling through a small tunnel.

'I was amazed by these caverns,' said University of Reading physicist Dr David Keating.

'The caverns vary in size but their resonant frequencies are very similar. They would amplify a fast drumbeat producing enhanced sounds and echoes during rituals, he added.

Dr Keating suggests that the caverns are designed to generate an acoustic phenomenon called Helmholtz resonance - the hollow type of sound created by blowing a stream of air across the top of an empty bottle.

Calculations suggest that drumming at two beats a second would have caused resonance. Inside the dark chamber with its stale air and presence of the dead, the enhanced sound would have produced an unforgettable experience for Neolithic man.