The World of Two Ears

Where a sound is, in six parts: left and right, an orbit around the head, near and far, the confusion of front and back, a turning gong and finally a blind direction test. The source is always the same sound; only the way it reaches the two ears changes. Headphones recommended. There is no claim of any effect.

Why this order? The first stage is horizontal direction: the sound first stays in the centre, on the left and on the right, then circles the head with turns of 50 and 25 seconds. The second stage is depth: distance changes through level, treble and reverberation together; then come mirrored directions in front and behind, where the arrival difference at the two ears is the same. The third stage is motion: a gong whose direction never changes turns once every 5, 4 and 2 seconds; finally the sound plays on the left, in the centre and on the right (±60°), with an 18-trial blind test in the panel. The source is the same sound in every part; direction is given by an interaural time difference of at most about 0.66 ms and the head's shadow. This model has no outer-ear filtering, which is why front and back can be confused.

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