Echolocation in Terms of "Reverb"

Image by Northeast Indiana via FlickrLet's look for a second, at echolocation as it would be viewed by a musician. Every different room, every environment, indoor, outdoor or otherwise has it's own acoustical properties. These would be known to musicians as that room's reverberant properties, or it's "reverb". Certain rooms are said to have a certain type of reverb. Rooms with hard flat parallel walls generally have what is considered to be "a lot" of reverb, where rooms with softer (more absorbant) walls that are oddly mishapen are said to have less reverb, meaning that the sound is not as likely to bounce around as much. A highly reverberant room is labelled such because the sound waves are likely to bounce off of the walls, sometimes several times before making their way to the listener. This gives the effect that one short tone is stretched out over a longer period of time. Essentially, the reverb is made up of many very quick echoes from nearby structures.

You have undoubtedly experienced and are familiar with certain reverb characteristics. For example, if you are in a quiet environment and you close your eyes and snap your fingers, you will immediately be able to tell if you are in a bathroom, car or auditorium. If you thought about it a little longer you could probably guess if the floor was carpeted and what the walls were made of.

Since the exact shape of any room give it it's reverb, this is essentially the same thing as echolocation. Save for one small detail, movement of the source and reciever (sound source and your ears). A room can have reverberant qualities and you may be able to make generic assumptions about the make-up of the room by listening to a sound, but without moving the source and reciever you would be hard pressed to tell the shape of the room or identify any objects in it.

Once we move, we gain another dimension of information. The "echoes" which are making up the reverb we are listening to as we click to echolocate, are changing direction as we move our head. It is not one click that gives us the information we require, but rather the difference between one click and the next which tells us how objects are moving with respect to us, and therefore how we are moving with respect to these objects.

If you have watched people echolocate, you will notice that they move their heads from side to side, tilt their ears and walk around objects in order to distinguish what they are. They are taking the information differential between clicks and piecing it together like pieces of a puzzle. It may take several clicks before someone is comfortable in their surroundings or can identify an object. I would think it to be nearly impossible to gather much environmental information with just one click no matter how good versed you are in echolocation.