SYDNEY, July 8 (Xinhua) -- Australian marine scientists believe they have discovered a new population of rare whales by zoning into their distinctive songs using underwater bomb detectors.

The researchers, led by scientists from the University of New South Wales (UNSW), used high-tech underwater microphones to record the elusive mammals' communication.

"We've found a whole new group of pygmy blue whales right in the middle of the Indian Ocean," said UNSW Professor Tracey Rogers in a statement released on Thursday. "We don't know how many whales are in this group, but we suspect it's a lot by the enormous number of calls we hear."

Rogers said the species were only "pygmy" in comparison to other members of the blue whale family, as they can grow to a length of about 24 meters.

The discovery findings, published in Scientific Reports, were based on audio data collected by the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO), a group that monitors international waters for nuclear bomb testing.

Rogers said an analysis of those recordings had yielded a surprisingly strong sound, a unique whale song.

After studying the song's structure, frequency and tempo, the researchers realized it belonged to a group of previously undetected pygmy blue whales.

Rogers said if visual sightings confirm this new population, they will become the fifth population of pygmy blue whales known to inhabit the Indian Ocean.

"Without these audio recordings, we'd have no idea there was this huge population of blue whales in the equatorial Indian Ocean," she said.

Bioacoustician Dr. Emmanuelle Leroy from UNSW said the team had scanned 18 years' worth of CTBTO data to realize that "thousands of these songs were being produced every year" and "formed a major part of the ocean's acoustic soundscape."

"The songs couldn't have just been coming from a couple of whales - they had to be from an entire population," Leroy said.

Leroy compared the songs' acoustic features with those of other blue whale song types known in the region, but the evidence pointed towards this being an entirely new population, which they have named as "Chagos" after the archipelago they were detected nearby.

"We suspect that the whales singing the Chagos song move at different times across the Indian Ocean," Rogers said.

"We found them not only in the central Indian Ocean but as far north as the Sri Lankan coastline and as far east in the Indian Ocean as the Kimberley coast in northern Western Australia." Enditem

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