Stealthy microphone intelligent machines (robots) could improve ocean noise maps

For conservation efforts, researchers believe, understanding ocean noise is important.
A robotic glider with a microphone captured a cacophony of sounds from vessels, whales and underwater explosions, moving slowly and stealthily across the Pacific Ocean.
The journey of the glider over 458 kilometers off the coast of Washington and Oregon and down to 650 meters demonstrates that gliders could be effective tools to help map the rates of ocean noise, researchers report in PLOS ONE on November 20.
The accuracy of the 18-day recording of the glider in July and August 2012 was confirmed by separate audio recordings from nearby microphones hanging from the water surface.
Stationary microphones, however, can not capture the full array of sounds in large swaths of the sea or at different depths in the water column the way a glider can, though, the researchers state.
Ocean noise is “something we need to measure and try to better understand why that’s happening, where it’s happening, and what the impacts are” to wildlife and marine ecosystems, Oceanographer Joe Haxel said on the coastal campus of Oregon State University in Newport.
Scientists typically eavesdrop underwater with hydrophones, waterproof microphones moored or dangled from the surface, or mounted on large ships capable of drowning out other sounds and scaring off marine life.
The slow speed of the glider just over 1 kilometer per hour and the quiet movement make it possible to sneak through the water picking up ambient noises.
A pump moves oil into and out of the bladder of the glider, affecting its buoyancy and causing it to float or sink in the column of water. These changes in depth propelled the glider on a slow, meandering path forward.
Haxel says, “The glider is good because it’s noninvasive,”.Hexel added, “It’s coming in on stealth mode.”