What is virtual sound and do I...

[karmazyn1]

.....turn it on if I already have 3d sound enabled on my headphones?

[ろらｴ]

The virtual surround in this game is a natively binaural audio mix option. Binaural audio if you haven't heard of it is stereo audio designed for headphones which recorded in a way that takes into account the way the human ears hear sound. The recording is recorded with two microphones that 'hear' the sounds being recorded much like the human ears head sound around them, which gives the recording an authentic 'surround' experience.
https://www.youtube.com/watch?v=IUDTlvagjJA

'Surround Sound' enabled Headphones, along with more widespread options like Windows Sonic for Headphones, DTS:X for Headphones and Dolby Atmos for Headphones all attempt to do the same thing and use multi-channel audio signals to approximate the effect of binaural audio recording. You do not need any of these options turned on to take advantage of a NATIVE binaural audio mix or recording, just like you don't need to enable them to hear the binaural effect of that Youtube video.

Resident Evil games are some of the only ones to do full native binaural audio for headphones, so turn off your 3D audio settings and let the game do it. The end result is far better.

[PC2070]

I'd suggest turning off one or the other (preferably leaving Virtual Surround Sound on in-game), having both on will mess up the way audio sounds