Perceptual Safety-Nets

We use interaural cues to locate acoustic stimuli, but this information isn’t always so clear. How might one disambiguate information presented within these “cones of confusion”? And why are we not always confused about a sound’s location?

As Blake points out, there are a few simple ways that we naturally resolve a sound’s location when the “cones of confusion” created by IID and ITD interfere. The first is head movement: moving your ears out of the cones of confusion and re-orienting them in respect to the sound source will allow IID, ITD, the pinnas, and other mechanisms to work.

There are other subconscious cues not involving the ears that allow us to locate sounds. One is context. One of the areas where IID and ITD become confused is distinguishing sounds from directly behind and directly ahead. If you sleep with your face toward your alarm clock, for example, your ears won’t be able to tell you if the alarm is ringing from in front or behind your head; but familiarity allows your brain to compensate and tell you that the alarm is, as usual, in front of your face.

Another cue is another sensory system: vision. Vision allows us to see our environment and possible sound sources, and match the sources with specific objects. Vision can even correct mislocalization of sounds by the ears, as sound waves may bounce off surfaces before reaching the ear while light from objects goes directly to our eyes. However, the strong influence of vision over hearing can sometimes confuse perception, as shown by the McGurk Effect.