You couldn't have had better timing to ask that question. I was just browsing instructables and found this just a few minutes ago: www.instructables.com/id/How-To-Make-A-CRT-TV-Into-an-Oscilloscope/ I am not completely sure if this is what we need because it doesn't tell us exactly what frequency it is, only shows us what it looks like, if that makes sense. I am sure we can find a better DIY but this just seems like the fastest way. Anyway, the way I see it, there are several frequencies being emitted from the guns, like sound coming out of the barrel, the trigger, the magwell, etc. You would need to find every single one and that might be too much work. One more thing; this thread was really meant to talk about silencers, not silencing your gun. You should have made a thread in the concealment section probably.