Ocean soundscapes as varied as landscapes

Underwater soundscapes are as varied as landscapes, according to acoustics researcher Dr Iain Parnum.

Dr Parnum gave a presentation for the Western Australian Marine Science Institution’s Thinking Blue school outreach program about marine soundscapes, which are a growing area of research interest.

Dr Parnum is a Senior Research Fellow at the Centre for Marine Science and Technology (CMST) at Curtin University and the Centre’s Deputy Director. He is also a Noise theme researcher on the WAMSI Westport Marine Science Program.

“In marine ecosystems, sound is vital to many species for navigation, communication and finding prey,” Dr Parnum said.

“For about 12 hours a day we have no light, so sound is important for a lot of marine life because sound waves are not inhibited by a lack of light.”

“But different areas of the ocean have vastly different sounds.”

He said there was an increased research focus on underwater soundscapes and the impact of noise on animals.

Dr Parnum said one of the soundscapes he had studied was the Perth Canyon, which is a deep submarine canyon 20 kilometres west of Rottnest Island. It is an important feeding ground for many animals and the area is also traversed by ships and other vessels.

He said between 2008 and 2016 an acoustics laboratory recorded the canyon’s underwater soundscape, including migrating whales, fish choruses and earthquakes, as part of a program designed to improve the understanding of noise and its impact on marine life.

Data from the sound recorders are used to create spectrograms which illustrate the energy, pitch and patterns of sounds.

“These then become an efficient way of monitoring the presence of these whales in the canyon and in other areas because we know their distinctive sounds,” Dr Parnum said.

He said Antarctic minke whales produced a noise, which submariners referred to as  ‘bioduck’ when they first recorded the mystery sound.

“Humpback whales meanwhile are the showoffs of the whale world and produce more complex songs with high and low frequencies.”

“The males will sing songs for hours at a time and elements of the song will be picked up and used by other pods.”

By understanding the various noises made by the whales, researchers have been able to identify when they are using the canyon.

“Pygmy blue whales are present in the canyon from November to June and peak between March and June.”

“The peak times for humpback whales in the Perth Canyon are June and July, during the northern migration and August to October when the species migrates south to Antarctica.

You can find out more about Dr Parnum’s work in Cockburn Sound here.

You can see Dr Parnum’s full Thinking Blue presentation here and find more information about the Perth Canyon acoustic observatory including access to the data here.