Exploring the sounds of the deep

Woody and Meg have been spending a lot of time on this ‘cruise’ listening for whales and dolphins. To do this they are using a hydrophone, which is an underwater listening device and towed a long way behind the ship so that we can’t hear the ship noise as loud (ships are noisy – especially their propellers that churn up the water to make them go fast – though the Discovery is actually fairly quiet for a ship).

Here is Woody with our hydrophone – you can see a clear tube – this contains the listening devices – there are 4 of them contained in the tube – 2 for listening for very high pitched sounds (like if you were talking in a really squeaky voices, or blow a dog whistle, and even higher than that – like bat noises – have you heard them? Not everyone can but the younger you are the better you can hear bats), and 2 for listening for a wide range of sounds. By using 2 of each, we can also tell direction (that’s why we have 2 ears on our heads so we can tell what direction the sounds are coming from – cool huh?!).

Here is Meg putting out the hydrophone – it takes about 10 minutes to put all 350m of cable into the water, we then connect it up to the cable that allows us to listen and record the sounds at our computer. Here are Meg & Woody listening to the hydrophone:

So what have we heard? So far we’ve heard pilot whales whistling so loudly I think they were trying to talk to us! Our cruise blog has a recording of these pilot whales - so have a listen :) We’ve also heard sperm whales – I’ll put a recording up soon (watch this space). Sperm whales are mega-cool - they dive down to the bottom of the sea (1km or more… that’s about 100 double-decker buses back to back or more) to catch & eat squid. But it’s pitch dark down in the deep sea, so sperm whales use sound to find the squid. Sperm whale heads are a third of their body (MASSIVE – their heads are around the size of a campervan) – they use these heads to make very loud click sounds, they echo off the squid allowing them to find them by the echoes. So it’s these sounds we can hear – they are very loud so we can hear them even when we’re not that close to them. Back to listening and more adventures soon.