Ringing Rocks Park is a state park in Upper Black Eddy, Pennsylvania at 40°33′47″N 75°07′37″W / 40.56316098204447°N 75.126893520355°W / 40.56316098204447; -75.12689352035522. The ringing rocks in that area are diabase. In 1965, geologist Richard Faas of Lafayette College took a few of the rocks back to his lab for testing. He found that when the rocks were struck they created a series of tones at frequencies lower than the human ear can hear. An audible sound is only produced because these tones interact with each other. Although Faas's experiments explained the nature of the tones, they did not identify the specific physical mechanism in the rock which made them. When the rocks are struck with a hammer or another rock, they sound as if they are metal and hollow and ring with a sound similar to a metal pipe being struck.
