i'm wondering how come simulating front,back,left and right source position on headphones is easy but up and down is not ? (maybe even impossible ?)

is it due to the shape of the ear ? but should we not be able to modify the input signal according to the shape of the ear and then simulate ups and downs movements ? why binaural impulses don't simulate correctly ups and downs on headphones ?



  • $\begingroup$ You have two ears. They can (relatively easily) detect differences in left/right. Since they are both on one level, up/down depends only on differences in frequency response from the shape of the ears. Simulating that is difficult. $\endgroup$ – JRE Nov 19 '19 at 10:29
  • $\begingroup$ @JRE Would you like to write your comment as an answer? See Should short answers be comments or answers? $\endgroup$ – Olli Niemitalo Nov 19 '19 at 10:51

Front/back is actually very hard too, at least for stationary simulation without head tracking.

The main reason is simple: Left/Right is done by looking at the differences between the two ear signals, i.e. interaural level differences and interaural time differences. If a source is located to the left, the sound will arrive earlier on the left ear and will be louder (depending on frequency).

In the median plane (front, up, back down), the ear signals are almost identical. The only information available are pinna cues, shoulder reflection, interaural changes due to micro rotations of the head, small asymmetries, contextual information, etc. . That's a lot less robust so the localization acuity in general is a lot worse. It's also harder to model since it depends a lot on the individual human and one-size-fits-all doesn't work well.


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