Perhaps this is part of the same as I notice Timothy Darvill has commented. I agree with his view.
Timothy Darvill, professor of archaeology at Bournemouth University, said that while sound played an important role in events at Stonehenge, the monument was probably not designed with acoustics in mind.
"The main structure is a replica in stone of what was normally built in wood," he said. "They used the same techniques. The positioning of the main components is all about the construction of a framework, a building if you like, as the setting for ritual adventures that included the use of the bluestones brought over from Wales."