I'm 100% certain it's related to the badly coded reverb in the game because we can hear the massive reverb on that sound. To my ears, COH2's reverb sounds cheap, metallic and poorly implemented (I have used DAWs and done my own mixing for my band and others so I've worked with a lot of software effects and sound design.)
A reverb is nothing but a series of echoes that are filtered. To do this digitally you feed the delayed signal back into the original.
We know COH2 has memory management problems. I start lagging at start after 4-5 games. What is probably happening is the bad memory handling is resulting in stuff getting stuck in the buffers for the reverb effect, producing an overload that results in a digital glitch. I think the reason that it's so much louder than the game sound is because the ambient effects subroutine is somehow not tied to the game master volume, it's running on the sound files and those sounds are controlled by the master volume so normally you shouldn't have an issue. But if the reverb/ambient subroutine is bugged then it's perfectly possible for that sound glitch to be louder than the rest of the game.
It's nothing like any glitch I've heard in any effect, and it's not the driver getting stuck (if this happens because of a CPU overload and the entire driver crashes you usually get a fraction of the last sound played infinitely, which sounds like a constant tone). I've never heard anything like this though when I was mixing and experimenting no matter how many reverbs I feed into delays into reverbs and so on...But software for musicians is usually better coded.
If you want to know more (sound design and coding is fascinating) try this article:
https://christianfloisand.wordpress.com/2012/09/04/digital-reverberation/