This has already happened. It's now controlled by the VON slider.

It could be worth testing this with the laser guided cruise missiles too. I had an incident a while ago where a missile was supposed to overfly my position en route to a laser target, but landed on me instead. I wrote it off as a fluke at the time, but this issue would perfectly explain it.

Interesting that you should choose now to complain about it, right after BI releases an RC branch adding the ability to choose the audio device in the game settings.

In T154335#2162486, @Fourty7 wrote:

Direct chat is affected by both VON & the Effects volume slider. You can think of it as a multiplier. If you set VON or Effects volume to 0%, direct chat will not come through. If you set both to 50%, direct would be at 25%, if you one to 100% and the other to 50%, direct would be at 50%, etc.

This was fixed and can be marked as resolved.

This was fixed at some point and can be marked as resolved.

In T156158#2154183, @dedmen wrote:

Easy to implement, pretty annoying to add to options menu though. So probably won't be done.

Still occurs in main branch 1.84.144923. And, as noted by Vdauphin, now also occurs when changing camouflage on the Prowler (Armed) and Prowler (Unarmed), with any camouflage. Oddly, does not occur on the Prowler (AT).

I really hope that "as designed" just means "there is going to be a sound but we deliberately haven't put it on dev branch yet" - because if the SPG-9 is supposed to be literally dead silent, then someone has made a poor decision. It's bad for balance and extremely bad for immersion and realism.

Reproduced on Windows 10 x64.