Thousands of years ago, ancient Britons built Stonehenge, but its true purpose has puzzled researchers for centuries. Could it have been a burial ground? A way to observe the night sky? Or maybe ...

The "reverberation time"—the time it takes for a sound to decay by 60 decibels—was about 0.6 seconds for mid-frequency sounds inside the model. This indicated that sounds inside Stonehenge ...