1. 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?
The duplex theory of sound localization for explaining sound localization attributes this ability to two different interaural cues which include interaural time differences and interaural level differences. The interaural time difference is a binaural auditory cue which is the minute time difference between when sound from a single source reaches the near ear and when it reaches the far ear. This slight time difference provides an essential cue to direction. The interaural level difference is the reduction in loudness that occurs when a sound reaches the far ear. With the head being in the way, it makes it difficult to calculate the correct interaural time difference and the interaural level difference since there may not always be a direct path for a sound to make it from a source to the far ear. This produces an intensity difference in the sound from one ear to the other. However, if a sound comes from anywhere in the median plane, which could cause the sound to reach both ears at the same time and with the same intensity, then the person will perceive the sound as being somewhere in the plane but often cannot tell where in the plane it actually occurs resulting in what is called the “plane of confusion.” In much the same way, the person experiences a “cone of confusion” for sounds when sounds come from one side of the median plane. In this situation the person is able to tell which side the sound comes from but is unable to differentiate among sounds that come from the many points on the surface of the cone. The confusion comes from the fact that all the points on the cone are equal distances from one ear than from the other which results in the same difference in stimuli at both ears. One way to overcome this is to simply tilt one’s head. This creates different temporal patterns of stimulation arriving at the two ears allowing people to differentiate among sounds that that would otherwise be unable to detect as far as direction is concerned.
