Question

Describe the problem posed by the “cones of confusion”. Start with the 2D example and then explain howit extends to the third dimension. Then, briefly describe two of the tricks used by our auditory system to solve the problem posed by the cones of confusion.

Answer 1

To determine whether the sound is coming from the right or left, the brain uses inter-ear differences in amplitude and timing. If the sound is louder in the right ear compared to the left ear, it’s probably coming from the right side. The smaller that difference is, the closer the sound is to the midline (i.e the vertical plane going from your front to your back). Similarly, if the sound arrives at your right ear before the left ear, it’s probably coming from the right. The smaller the timing difference, the closer it is to the midline.

Inter-ear loudness and timing differences are pretty useful, but unfortunately, they still leave a lot of ambiguity. For example, a sound from your front right will have the exact same loudness differences and timing differences as a sound from your back right.

In 2-D, it is the angle in which the human ear is unable to find the location of the sound source.

In 3-D, a cone-shaped region originating midway between an organism's two ears, and radiating outwards, where a sound's location is indeterminate.

Not only does this system leave ambiguities between front and back, but it also leaves ambiguities between the top and down. In fact, there is an entire cone of confusion that cannot be disambiguated by this system. Sound from all points along the surface of the cone will have the same inter-ear loudness differences and timing differences.

Amazingly, we are able to do this because of the shape of our ears and heads. When sound passes through our ears and head, certain frequencies are attenuated more than others. Critically, the attenuation pattern is highly dependent on sound direction.

This attenuation is can also based on the heat transfer direction. As the sound heats up the air.