I made this sound recording of a frozen lake in the winter of 2005/06 in the area around Berlin. Frozen lakes are known to give off most noise during major fluctuations in temperature: the ice expands or contracts, and the resulting tension in the ice causes cracks to appear. Due to the changes in temperature, the hours of morning and evening are usually the best times to hear these sounds. In my experience, thin ice is especially interesting for acoustic phenomena; it is more elastic and sounds are propagated better across the surface. Snowfall, on the other hand, has a muffling effect and the sound can only travel to a limited extent. The ice sheet acts as a huge membrane across which the cracking and popping sounds spread. Underwater microphones proved especially well-suited for these recordings: in a small hole drilled close beneath the surface of the water, the sounds emitted by the body of ice carry particularly well. The most striking thing about these recordings is the synthetic-sounding descending tones caused by the phenomenon of the dispersion of sound waves. The high frequencies of the popping and cracking noises are transmitted faster by the ice than the deeper frequencies, which reach the listener with a time lag as glissandi sinking to almost bottomless depths.

I catched this take in Costa Rica on a canoe ride down the cano negro, a mangrove swamp with lots of water ways and channels. On this bit a howler monkey started growling on the left hand side of the water, while spider monkeys climbed through the forest canopy on the right. The beautiful call of the montezuma oropendola bird echoes over the water surface, then after some time a caiman jumps into the river.

The fur seal colony at Cape Cross in Namibia is very noise and smelly as well...

I made this recording at Sea of Galilee very close to the spot where Jesus was supposed to walk on water. I guess this must be what he heard at that excursion. By the way: scientific study has suggested that rare atmospheric and water conditions could have caused ice to form on the lake. The research shows a period of cooler weather swept what is now northern Israel from 1,500 to 2,600 years ago. Sub-zero temperatures could have caused the formation of ice thick enough to support the weight of a man.

Glacial ice consists of snow that has been extremely compressed and compacted. In the case of the inland ice in Greenland, this process may stretch over thousands or even millions of years before the ice is pushed into the sea by a glacier. As the layers of snow pile up, tiny bubbles of air are trapped and put under enormous pressure by the weight of the surrounding ice. When the glacial ice finally melts in the sea, these tiny bubbles of air are released with a quiet, explosive popping noise, adding up to a many-voiced sizzling. The icebergs that drift in the Arctic give off a constant sizzling sound which is loud enough to determine their position from under water. The phenomenon was first noted by the crews of submarines. It is also known as “bergy seltzer” due to its resemblance to the sound of fizzy drinks.

I recorded the audio excerpt in Greenland 2006. I collected some ice chunks from icebergs in a plastic bag during a ship tour and stored them in a bar for some hours before returning to my hotel room. Surprisingly the ice was not melted, there was not even water in the plastic bag. I put the ice scraps in the bathtub and recorded the sizzling with an underwater microphone.

On a husky sledging tour in northern Finland close to Inari I recorded the huskies in the evening after feeding for their occasional howling session.

A Mexico City soundscape, from the digital Westminster Chime of Torre Latinoamericana to street vendors and church services.

Mount Yasur on Tanna Island of Vanuatu archipelago is one of the worlds most active vulcanoes accessible to the public. This is a short excerpt of what I heard one night sitting on the rim of the crater.

The most spectacular Maya-site is probably Tikal in the Guatemalan jungle. I had the opportunity to stay at gran plaza in the center of the ruins about 45 min. before gates open at dawn. My guided group rushed to the temple with the best sight over the forest canopy, while I was alone with a lot of wildlife in the heart of this abandoned city. There are a lot of parrots, beautiful calls of the montezuma oropendola, a Guatemalan turkey and - indeed - the notorious howler monkeys.

On a boat trip to Kangerlua glacier in close to Ilulissat a fin whale suddenly crossed our route and spouted its characteristic fountain through the blow hole in front of us. I immediately dunked my underwater microphone in the water and recorded with another normal mic on the second track. The whale dissappeared and there was not a single tone underwater. It took about 3 minutes and the whale reached the surface again, this time making a singing tone while breathing out on the surface. I never heard that whales make sounds on the surface, so my surprise was great and even more, when a moment later one iceberg around started calving and tumbling in the water, which I was able to hear over my headphones via the underwater microphone.