This was annoying me too, and I found this thread. I came up with a solution using an AutoHotkey script. It simply lowers system master volume to 5% when hitting some of the external view F keys, then back to 100% when hitting F1. Here's the script:
isSoundLow := false
#IfWinActive ahk_class DCS
F2::
F3::
F4::
F5::
F6::
F8::
F11::
if (!isSoundLow) {
SoundSet, 5
isSoundLow := true
}
ChangeView(A_ThisHotkey)
Return
#IfWinActive ahk_class DCS
F1::
SoundSet, 100
ChangeView("F1")
isSoundLow := false
Return
ChangeView(Key) {
Send, {%Key% down}
Sleep, 20
Send, {%Key% up}
}
If you're not familiar with AutoHotkey, you just have to install it, put that script in a .ahk file, and run it.
edit: hmm just realized, this doesn't solve the problem of going to external view when you get killed for example. Oh well.