June 26, 2019
Noise pollution threatening the normal behavior of the marine
For whales and dolphins, ‘listening’ is as important as ‘seeing’ is for humans, as they live in a world of water and sound. Noise pollution threatens whale and dolphin populations, interrupting their normal behaviour, driving them away from areas important to their survival and at worst injuring or sometimes even causing the deaths of some whales and dolphins.
Loud underwater seismic surveys (pulses of noise sent down to the seabed) to locate oil and gas, military exercises using powerful underwater sonar, and increasing levels of boat activity all create an ocean full of noise. And levels are increasing.
Ambient noise is generally unwanted environmental background noise which clutters and masks other sounds. The main causes of noise in the marine environment are (a) shipping and other man-made (anthropogenic) noise, (b) sea state noise (water motion), (c) seismic noise (from volcanic and tectonic activity), (d) marine life and (e) thermal noise.
Different noises have characteristic signatures including frequencies and ranges of sound pressure levels. Low frequency sound takes less energy to create and to keep moving. As a result, it is not interrupted easily by outside forces and travels further. A high frequency sound takes a lot of energy to create and a lot of energy to keep it going. Because of this, it is easily interrupted by outside forces and does not travel a far distance. This means that the whistles and clicks of dolphins can easily be masked by other sounds in the oceans.