Well, I must admit I have a weird sound settings combo, but it works for me.
Here is a screenshot of my in-game sound settings, but note that WoT is set to only 10% in windows Volume Mixer (screenie 2.)
That way there is noting coming from WoT that could startle me.
I am on Windows 10 though. Not sure if you can change per-app volume in Windows 7 Volume Mixer.