Sources of Noise

Since the industrial age, man-made ocean noise has increased steadily; and we're creating new noisemakers all the time.


Perhaps the loudest new noisemaker is US Navy's low frequency sonar. In 1994, just a few miles off the California coast, the navy began testing this extremely loud sonar in an exercise called Magellan Sea Trials. The Natural Resources Defense Council, an environmental watchdog group, estimates that sounds during Magellan were about 240 decibels. That's 30,000 times as loud as ATOC's loudest.


At any one time there are 127 supertankers at sea, each generating 187 dB of low frequency sound. That's as loud as some military artillery explosions. These ships give off even louder sounds at lower frequencies. Icebreaking ships, dredging boats, oil drilling rigs, sonic oil exploration and dynamite explosions from construction and demolition projects also add to the undersea racket. dB = decibels, a logarithmic unit of sound pressure - when measured under water-one meter away from the source (Note: decibel levels on this page are normalized to 1 micropascal, a standard used in underwater sound measurement.)
Large tanker 177 dB A continuous noise on shipping pathways all over the world
Icebreaker 183 dB A cycling noise primarily in Arctic Ocean, north of Canada, Alaska, and Russia
ATOC experiment 195 dB Sound pulses are emitted from a single source off the California coast
Low frequency sonar 235 dB Continuous pulses at undisclosed locations, potentially worldwide
Supply ship 174 dB Continuous sound emitted along shipping lanes all over the world
Seismic oil exploration 210 dB Low pitched pulses of sound, generated in oil-rich ocean areas world wide
Dredging boat 167 dB Creates continuous, low frequency grinding, in near shore construction areas

Natural Ocean sounds

Wind and waves ~85 dB
Earthquake 95-135 dB
Harp seal call 130-140 dB
Bottlenosed dolphin ~150 dB
Humpback whale moan 175 dB
Gray whale moan 185 dB

Because the sound diminishes more quickly in the water, it's not completely accurate to compare sound levels in the water to levels in the air. Use the chart below to help you imagine how loud the above noises would be if you were listening near the source.

Sound levels in air dB
Rocket launching pad 205 dB
Rock band (near speakers) 145 dB
Jet flyby 300m overhead 135-145 dB
Chain saw, pneumatic drill 125 dB
Motorcycle, lawnmower 115 dB
Hair dryer, noisy restaurant 95 dB
Light traffic, 100 ft away 75-85 dB
Refrigerator 65 dB
Quiet residential area 55 dB
Quiet library, soft whisper 55 dB
Wilderness area 50 dB

Sounds above 90 dB can damage the human ear after extended exposure