The noises are weird to say the least. The Ross seal sounds like a spaceship zipping into the unknown. The ice could be an opera singer doing vocal exercises. The crabeater seal might pass for an electric drill. The minke whale oinks like a pig. Most disconcerting of all, a collapsing ice shelfA large floating platform of ice that extends from glaciers on the ground. resembles a heavy drumbeat. 

These are among 50 recordings of rarely heard sounds collected by two acoustic laboratories in Germany. They come from underwater microphones which were attached to floats and left in the Arctic and Antarctic for two years.

"We probably think we know what the poles sound like - but often that is imagined," says Dr Geraint Rhys Whittaker, who works at the Helmholtz Institute for Functional Marine Biodiversity and the Alfred Wegener Institute.

The sounds of polar animals are hard to capture because of the huge distances they cover in freezing conditions. Ross seals, for example, live on pack iceIce that is floating in the sea and not attached to the land. in the open seas - but the floating microphones were able to record five different calls.

They also captured ice "singing": the noise of ice moving in water, contracting, or melting and refreezing. Some of the sounds, though, have been completely unidentifiable.

Alongside the natural ones are those made by human beings - and their extent is alarming. Seismic blasting, which is used to locate oil and gas fields, involves firing extremely loud airguns into the ocean bed. The sound can travel for up to 2,500 miles,¹ driving marine creatures away and disrupting communication between them.

Sound is far more important than vision for these creatures, since they live largely in dark water. The noise from shipping, dredging and naval sonarA way to find objects underwater by sending out sound pulses and measuring how they return after being reflected by items. can also be confusing and damaging: it has been blamed for whale strandings and separating mother whales from their young.

Another highly disturbing noise is that of collapsing ice shelves, believed to be the result of global warming.

The melting of polar ice not only raises sea levels but reduces the amount of heat that the ocean can absorb, leading to even more warming. It also reduces the salt content, allowing soundwaves to travel more quickly.

Marine ecologist Ashlee Lillis found that warmer water increased the noise made by snapping shrimp as they open and close their claws. "If you're a fish that needs to talk to the other fish," she says,² "or use acoustic communication for mating or whatever, then it might actually be a big bummer to suddenly have a lot of shrimp making noise and masking [other sounds]".

Geraint Rhys Whittaker hopes that the new recordings will awake people to these problems. He has been working with the group Cities and Memory to incorporate them in striking musical compositions.

"When sight is impossible," the group notes, "acoustic data can give scientists invaluable information on breeding habits, migration patterns and the ways in which human-made noise negatively affects marine environments."

Yes: These noises give us a vivid idea of the impact humans are having on the polar regions. As Alanna Mitchell writes in Canadian Geographic: "Earth is singing a strange and troubling song."

No: The noises are very interesting, but they are just noises. We may have worked out how different species communicate with each other, but we are far from working out what they are actually saying.

Or... We are very much a visual species, and what we hear rarely has as strong an impact as what we see. Film of collapsing ice shelves affects us much more than the sound of them ever will.