Stone Age Sound

Strange passage graves, over 5,000 years old, can be found in Ireland. They're older than Stonehenge, and just as mysterious. Who built them? How did they build them? Why are they such a strange shape?

Joanna Pinnock investigates these graves, whose passageways and chambers, with strange carvings on the walls, were built to align with the sun.

Two researchers, Aaron Watson and David Keating, have an exciting new theory to explain the shapes and layouts of these Neolithic structures. They think that whoever built them deliberately arranged them to provide a phenomenal auditory experience.

Sounds of drumming and humming would be amplified in some areas, deadened in others and make religious rituals dramatic affairs.

The programme joins the researchers on site at Newgrange passage grave to test their intriguing theory.