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Latest from the Gunsmiths Bench

Suppressor sound testing last week with our new purpose-built microphone mounting fixture. With this setup and running four B&K2209 milspec sound meters at the same time, we can get readings for ‘Milspec muzzle’ left and right, and ‘Shooters ear’ left and right for every single shot fired. (The meters then have to be manually reset after each shot.) To the best of my knowledge this is currently the best suppressor sound testing set-up available in this country. I am aware of guys running up to 2 meters at once, but no-one has done 4 at once before. 

The old analogue Bruel & Kjaer meters have been a mainstay of the suppressor testing industry for the past 40 years, and they are still one of the few portable sound meters available that are capable of recording peak sound level with a fast response time of less than 20 microseconds. This is vital to be able to capture the actual true peak of the gunshot sound/pressure impulse. Anything slower than this does not meet the spec, and cannot be trusted for accurate results.

Video here is of 5 shots fired with an unsuppressed .17HMR with a 20″ barrel. Just so you can see how loud the impulse noise actually is when you are measuring the true peaks. Guys trying to test with i-phones or other cheap non-milspec meters and getting readings around 105dB (for cartridges like this) or whatever are miles off from the true readings, because the device they are using is totally incapable of measuring short-impulse gunshot noise accurately. Publishing spurious and inaccurate sound-test results from mobile-phone aps or cheap hand-held meters only mis-informs others about the performance level of what they are claiming to test.

More videos to follow soon……

(Edit: just for clarification the sound meters are all set for ‘A-weighting’ for the dB readings, which is the US standard accepted practice. European tests often use ‘C-weighting’ which may provide different readings at certain pressure ranges. Anyone comparing results from A-scale or C-scale test results needs to be aware of this. Also, in the video commentary I thought it was an 18″ barrel, but it is in fact a 20″ barrel. Rifle was kindly loaned from a friend for the test.)

Average of 5 shots for each meter (Unsuppressed shots) Milspec muzzle left – 156.56 dB(A). Milspec muzzle right – 157.06 dB(A). Shooters ear left – 142.08 dB(A). Shooters ear right – 142.10 dB(A).