Lligwy "Burial Chamber"
It was a lovely day when we visited this site, which is always fortunate when you have a toddler in tow. We got left to ourselves apart from someone who showed up after I had done most of the work. To cut to the chase on the experiments, I found an area which seemed to be the most "live" on a handy ledge in the chamber. It seems that getting the source of your sound as near as possible to the stone also helps. CADW's (Welsh Heritage) book on the ancient monuments of Anglesey says about Lligwy "This great capstone is about 5 feet (1.5m) above the bottom of a natural fissure in the limestone rock, and the supporting uprights sit on the edge of the fissure or on rough stone walling". Perhaps these fissures are where the earth's natural charge is greatest, as according the piezoelectric theory, the rocks must already have a tiny electric charge in order to convert the sound into greater electrical energy.
I had prepared a CD of didgeridoo samples at different pitchs to experiment with, to see which pitch produced most electricity. Here are the results. Evidently pitches in the region of E-F produce best results, although when switching to a low G, there was also a surge.
Please note that the stones respond slowly in terms of both input / output of electricity. It takes a minute or two of silence until the charge drops off. This explains why they are still "live" during moments of silence and why it is possible to get a reading after the music has stopped. What amazes me is the way the voltmeter keeps time with the music.
Here is Lligwy responding to a song called "Uluru Legend" by native Australian group "Legends of Uluru", where the didgeridoo is pitched at F. You can hear Rosie attempting to join in.
These stones are beautiful in appearance. The cap stone is huge and has deeply furrowed grooves around the edges. I was hoping to get some comment from Andis Kaulins as to which constellation(s) are represented. The dots and dashes on the sides of the cap stone appear to be a map of stars as taken in a line at particular degrees. This won't make any sense at all if you don't know anything about basic astronomy and I am very much a beginner myself! From what I can make out it represents Cetus and surrounding stars.
The chamber is accessed through a small entrance which it is possible for the average able-bodied human to enter. It is not possible for most people to stand up in there. It was very uncomfortable work for me, but the results made it worthwhile.
Here is the plan of the chamber from the CADW notice board.