In the PS2 game, Silent Hill 2, the instruction manual mentions the game used “S-Force” sound to produce a surround sound type effect out of 2 speakers. Here is a quick article about it:
http://www.sony.net/SonyInfo/News/Press/200103/01-015E/
Anyways, in all my searching, I couldn’t find how they accomplished this, or how accurate the effect is. Anyone know?
The magic term in that press release is HRTF - Head Related Transfer Factor. As I (coincidentally) mentioned in a recent posting about the shape of our ears, HRTF is the mathematical expression of how the ridges in our ears interact with sound to scatter and delay the sound so our brains can process and determine where a sound is coming from.
What Sony’s doing (and they’re not alone, and definitely not first) is passing an audio signal (more likely, this is being done at a digital level, rather than analog audio) through some HRTF filters, so the sound comes out of the speakers with exaggerated positioning clues mixed in.
Two other notable “2-speaker surround” systems are QSound and Dolby Virtual Speaker.
Excellent, thank you very much. Could you perhaps elaborate on the “exaggerated positioning clues mixed in” portion though? Also, how convincing is the effect?
I’m no whiz at psychoacoustics, so I can’t begin to guess how they actually produce the location clues. I just know it involves tweaking the timing and phase of sounds. As such, it is somewhat dependent on how well your speakers are set up.
As for the effect, it can be very convincing. I recall an X Files episode a few years ago (they started using QSound in 1996) that involved something approaching from behind. It really sounded like it was behind me. eeeeek! :eek: