A latest research has suggested that noise generated by shipping traffic in the Salish Sea extends into the same frequencies that local salmon-eating killer whales use in hunting and communication.

The focus of earlier research has been on low-frequency noise pollution generated by container ships and its impact on balleen whales, latest underwater sound measurements noted in the Strait of Juan de Fuca and Puget Sound have disclosed that ships have also been generating high frequency noise, travelling much farther than earlier believed.

Lead author Scott Veirs of Seattle’s Beam Reach Marine Science and Sustainability School said that Orcas find their prey by sending out clicks and hearing the echo, a process that may get disturbed by shipping noise.

The researchers fixed hearing instruments in the critical habitat of the southern resident orca population calibrated for a broad range of frequencies, which included the ones used by the toothed whales in communicating.

Veirs said, “If you listen, you quickly learn that whales are wonderfully vocal, but also that their environment is filled with ship noise”.

Veirs added that scientists had supposed that the type of noise made by shipping traffic wouldn’t intervene with orca communication because the vibrations were below the frequencies that the whales use. It turned out that the researchers were listening from quite a long distance.

The latest data has revealed that high frequency noise is generated by propellers when they turns faster than they have been designed to run, however, the vibration dissipates over nearly 5 km.

The researchers noted and compared noise from 41 distinct types of ships making 2,809 trips through the Haro Strait, nearly 50% of which were composed of container ships and bulk carriers. Veirs said that though low frequency noise differed by ship type, all vessels made notably high frequency noise, and whale watching boats were among them.