Dr Merchant studies noise levels in the seas around the UK. He and his team recently produced a detailed map of where the cacophony is greatest. However, while it is difficult to confirm exactly how noise levels have changed in recent decades, he says they have probably increased overall.
“The answer to that is almost certainly ‘yes’,” he says.
He points out that there are other significant sources of noise pollution at sea. These include noise from shipping, where, for example, propellers slicing through the water create a wake and with it a mighty rumbling sound that can travel for hundreds or even thousands of kilometres.
Then there are offshore wind farms, which rely on pile-drivers that bash huge columns into the seabed to create the base platform for turbines. Engineers on such projects also occasionally have to clear unexploded ordnance left behind, for instance from World War Two.
Detonating a bomb underwater creates a lot of noise but the bang can be softened by using a device to create a curtain of bubbles around the bomb.
Wind farms in the UK licensed to use bubble curtains for this purpose include Hornsea One and Two off the north-east coast. Currently under construction, the full Hornsea complex will eventually form the largest offshore wind installation in the world.
Marine biologists continue to hope for technologies that will make human activity in the oceans quieter. Dr Jessopp acknowledges that seismic air guns are cheap and have been proven to work. With marine vibroseis still not available at a commercial scale, firms may not see any reason to change how they do things.
“In the absence of any real viable alternative we’ve just kept doing it. It’s kind of business as usual,” says Dr Jessopp.
So the seas will remain noisy for sometime and whales will have to continue to shout to be heard.