Sonja recording bird song.
We had a wonderful few hours at the Listening Wall at the Loons. An extraordinary experience. You have to stand on the 'sweet spot' in the middle of the parabola and amazingly the sounds are magnified. The wall was inspired by the World War II concrete walls dubbed 'listening ears', or acoustic mirrors used along the south coast of England to give early warning of approaching enemy aircraft before they were visible. Radar made them obsolete. http://www.andrewgrantham.co.uk/soundmirrors/
The sweet spot.
Here below is Sonja also recording night sounds at Brodgar. What we called her Caspar David Friedrich pose.