Can a subwoofer create a surround sound on a stereo system?

So I bought myself 2 speakers and a subwoofer and was playing a game. Its not a big subwoofer, but gun shots and explosions sound amazing nonetheless.

The game I was playing was Crysis 1 and at some point I was shooting at 2 north koreans while I heard a third one shouting something right behind me. I actually got scared for a second since I never had any sort of surround devices and I looked back, then I realized its the game, turned my character back and shot him.

The subwoofer is under the desk in front of me, as are the speakers (well, the speakers are ON the desk). My guess is the bass of his voice traveled behind me since the subwoofer sounds bounce around walls?

Is that what happened, or am I crazy? I will have to try it again but havent gotten around it yet. Anyone knows how to explain?

PS: I know that stereo sound can still give you a decent aproximation of where the sounds behind you are coming from, but that was different because I heard it like someone was right behind me in the real world.

Most of the sound you hear in a room is reflected off the walls, ceiling and floors. Our ears are quite good at picking out directionality from sound though, despite these reflections. Although bass is somewhat directional, I don't think sound apparently coming from behind you has anything to do with your subwoofer.

I'd think it has more to do with pseudo 3D encoding done on the stereo output of the game. This 3D audio encoding changes the nature of sounds (phase, frequency, delay, etc) and 3D sound processing is included with versions of CryEngine. Using such techniques it is possible to create stereo sounds as if they are coming from behind you.

"Vanilla" stereo mixing (without 3d sound processing) does not really give any indication of sounds coming from behind you, but is supposed to present a "sound-stage" in front of you, with sound filling the gap and/or imaging sounds between your stereo speakers (when properly positioned).

If anything, a subwoofer (being mono) would reduce any stereo effect of low frequencies. Many people tend to perceive directionality more at the higher frequencies, so having a subwoofer does not matter to so much to them.

Yeah, somehow your room conspired to reflect some sound back at you from behind. An acoustic quirk. Lower frequencies of sound (bass) tend to be absorbed or pass through objects and don't reflect as well as higher frequencies, so your subwoofer probably has nothing to do with it.

There are also audio processing techniques that mimic the way our ears perceive sound from in front and behind that can make it seem like a sound is coming from in front of or behind us, but in my experience, they're only minimally effective.

That, or you've got a secret cadre of North Koreans in your house.

Like the others have said, sound can (sometimes) reflect off of floors, ceilings, walls, creating a surround sound effect. Even my shitty laptop speakers, from time to time, have achieved this. It is no where near as consistent (or of the same quality) as having a proper surround sound set up.

Yeah it's a quirk, its a trick that many virtual surround sound systems take advantage of. But yeah a Sub Woofer will not create the illusion of surround sound especially as Bass Frequencies tend to get absorbed by everything (which is why bass travels so damn far)

I'd wager Crysis has a pretty good sound system. I'm not good enough with this terms to really be able to describe it in detail - but stereo can do depth pretty well as long as the source is configured to take advantage of it - first and foremost you can position a sound by playing it in both speakers, but at a slight, millisecond delay in one of them, and changing the sound's phase and add reverberation can strengthen the effect. I don't know if your radio station ever used to do the stereo speaker tests, but radio here used to do that when FM radio became common (late 70's) and continued doing it up until the early 90's - first left speaker, then right speaker, same sound from both speakers, and then phased stereo to make it sound like it came from across the room. Back in the 90's most games couldn't do this, I think Battlefield 1942 was among the first to really attempt to do phasing and doppler shifting, and that sounded great using stereo speakers.

Your subwoofer is probably not doing a lot of this work, but your regular stereo speakers do.

PPl. are giving you the right answer, directionality is to some extent done by some wizardry of sound processing, though to actually be back behind you I thought you might need rear speakers. But I suppose it can be faked with fade and what not. Enough to make you look!

But subwoofers, as opposed to base speakers as they used to be in the cabinets, are in one place. Hard to do anything with that, though higher parts of the sound may be positioned in the other 2 speakers. Maybe still get that explosion behind you and off to the left...

Subwoofers generally don't play sound in the vocal range of frequencies. Like others have said it's likely some 3d sound processing or your just imagining things.