Despite a previous entry, I’m not obsessed with the human sense of hearing. However, I did come across some interesting research that (eventually) lead to this story, which I shared with listeners of ‘Einstein-A-Go-Go’ a couple of weeks ago.
The phrase “echolocation” was first coined in 1944 by Donald Griffin (Harvard University), while he was investigating the navigational behaviour of bats. Of course bats are not the only animals to use this technique. Toothed whales (such as dolphins, porpoises, orcas and sperm whales) also use echolocation, as some birds, shrews and tenrecs. Some of the sounds are at frequencies that are audible to humans and some are not, but that’s ok – they’re not usually talking to us.
The idea of echolocation is that the animal makes a sound; if the sound waves collide with an object, they will bounce back (or echo) and are detected by the animal. The delay between when the sound is emitted and the detection of an echo indicates the distance of an object. Animals that use echolocation may emit sounds from their mouths, or from specialised organs in the nose or head (I especially like the “melon” that features in the head of toothed whales).
Technologically, the human equivalent of echolocation is SONAR (SOund NAvigation and Ranging), used most notably by submarines. The first active SONAR systems were developed by 1918. So interestingly, the development of SONAR preceded the discovery of echolocation by humans, but as is often the case, nature had got there first.
The evolution of echolocation has had some interesting twists. In 2008 Nancy Simmons et al published research (Nature 451, 818-821) showing that the earliest known bats did not have the morphological hardware to echolocate and that they probably developed the ability to fly first. Presumably they were able to sense the environment around them using passive audio signals as well as visual and olfactory ones. Either that or they simply flew into things a lot.
Some humans have learnt to use echolocation as well. Daniel Kish is probably the best known case. Daniel is lead founder and CEO of World Access for the Blind, and trains other blind people to use echolocation.
Now a team of Spanish researchers believe they have developed a series of tests to help unlock other human’s echolocation abilities. Juan Antonio Martínez says that in a couple of hours a day for a few weeks anyone can learn how to echolocate using clicks. Martinez and his colleagues had their paper published in Acta Acustica united with Acustica. As well as aiding the blind, these techniques could also be useful for emergency workers operating in dark or obscured situations such as those encountered by firemen and rescue workers.
I’ve tried this a few times and it’s not easy, but you start to sense how it would work. I’m kind of looking forward to the next power blackout . . .