Fred Sharpe of the Alaska Whale Foundation presented findings on 18 May at the Astrobiology Science Conference in Madison, Wisconsin, showing that land-based microphones set up with local tip-offs recorded very low-frequency rumbles (like distant thunder) and previously undocumented pizzle, howl, and hooting sounds from humpback whales, audible up to 6 miles away. Sharpe postulates the thrums may originate in blowhole structures that seal against water during dives.