January 13, 2006

Holophonic sound: how do they do it ?

What is Holophonic sound, and how the heck do they  do it ? I've summarised my finding from the various sites I visited in search for an answer.


If you ask someone who understands GPS devices they will tell u that one needs atleast 3 satellites obtain a location fix in 2D, and atleast 4 to get a 3D fix. Human(and most of the animals from the animal kingdom) however, can do the same with just 2 eyes.


The human ear, similarly, has a remarkable ability to identify the source of a sound in three dimensions. But unlike 3D movies, which uses polarised glasses to show us movies from different angles to each eye, nothing similar existed for the ear for a long time. Stereophonic sounds which controls volume and channels to each ear have existed for a some time now. And if you have any home theatre system with more than 2 speakers you might have also heard surround sound effects in the comfort of your home.

If 2 cameras can accurately capture 3D images for the eye, why is it that 2 microphones and 2 speakers can't reproduce 3D surround sound ? I started pondering over this question when I first heard the holophonic mp3

The problem with the ear is that unlike the eye, the most complex part of the ear is unassuming that its easy to ignore its importance. For a true reproduction of surround sound using headphones, one has to take into account the contours of the ear which distorts each sound from different angles in a little different way. One way to do it is by placing migration phones insider a object which looks like head and has contours like the ear to distort the sound. The other way to do this, (which will soon invade the digital world if it hasn't already), is using mathematical models which can take a sound and its 3 co-ordinates as inputs and return a volume and delay for each ear. Its possible that such models already exist, however its not as widespread as it could be one day.