According tomedia, sperm whales use echolocation technology to search the dark deep ocean for prey such as squid — so competing sounds in the deep sea can undermine the process. A recent study suggests that even a new, improved artificial sonar can cause problems.
The study was led by Professor Patrick Miller, from the University of St Andrews in Scotland. Based on a previous study in Norway, miller’s team has shown that sperm whales stop foraging when they are exposed to pulsed sonar. Pulse sonar is a traditional sonar we see in movies, consisting of a series of sound pulses, with pauses. Like one of the users, the submarine uses it to listen for pulsed echoes during a pause.
A relatively new sonar technology, called continuous sonar, has emerged, unlike pulsed sonar, which emits a long-sound signal and simultaneously listens for the echo of the signal. This allows the user to detect the target more quickly without the need for a sound as loud as a conventional pulse.
Miller and his colleagues returned to Norway to test whether the new system could also be a problem for sperm whales. There, they tagged some whales with a data recorder connected to the suction cup, then followed them with a boat that towed a continuous sonic transmitter. Scientists keep a certain distance so that animals can hear sonar without damaging their hearing.
When analyzing the recorder data, the results show that, like pulsed sonar, continuous sonar can also cause whales to stop looking for prey. Interestingly, Miller found that greater sound energy (i.e. the total energy of the signal, including duration), causes more problems than the amplitude of the sound (i.e., the instantaneous loudness of the signal, independent of duration).
Therefore, scientists suggest that in order not to affect sperm whale feeding, the Navy should reduce the energy content of sonar signals.