Saturday, September 17, 2011

Head Related Transfer Function (HRTF)

After Space Football, I was asked to join Argonaut Software, initially to carry out research into 3-D sound in tandem with work Argonaut were doing with Nintendo into a Virtual Reality headset.

This research involved running the Head Related Transfer Function (HRTF) software on dedicated Digital Signal Processing cards in the PC. I learnt a lot about how our ears and brains (may) perceive sounds and the direction they are coming from.

As every person's ear has a different shape, in the ideal case, each person has their own HRTF measured.

This was achieved by putting small microphones in a persons ears and then recording the response of this microphone to real clicks (impulses) generated around the subject from different locations in space.

This then creates a 3-D impulse response map.

To use the HRTF to position a sound in 3-D via headphones you modify your source sound by the measured impulse response from that location in space.

Of interest was that the HRTF maps we had were of other people (we did not have our own taken), and initially this meant that initially people were not very good at pointing to where a sound was being placed by the software. Over time users "learnt" the other peoples HRTF's and became better at pointing to the intended location of the sound.

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