It seems that frozen lakes can actually be quite noisey. Not just crunching and creaking of ice, but much, much more.

When the conditions are right, rapidly changing temperatures, snowless ice, no wind, the entire ice sheet can resonate when minor cracks form. We discovered this a couple of weeks ago when it was a calm evening with the temperature dropping past -12C. There were very strange resonate boings coming from the direction of the lake. The noises were so loud at times that we could hear them up to 200 metres away from the lake edge. But standing on the jetty it was a different matter. The noises were coming from all directions all across the lake, just seconds apart. It was a very strange sound and quite freaky in the dark. They sounded so odd it was hard to imagine they were natural.

But as we found out later (thanks to Google), it is known, if not that common. And here are a few examples.

• http://www.vimeo.com/139013
• http://silentlistening.wordpress.com/2008/05/09/dispersion-of-sound-waves-in-ice-sheets/
• http://kalerne.net/joomla/index.php?option=com_content&task=view&id=138&Itemid=115

The lake was over 20cm thick at the time and extremely clear. That is easily thick enough to walk on, which we did the next weekend a couple of times. The lake even rewarded us with a few extra boings as well.