Another Interesting Cricket Sound Test

If you get some results do post them, I’d like to see how those guns of yours differ in noise level.

I actually need to install audacity to my new laptop so I’ll write some instructions while I do it.

We’ll start by downloading audacity from http://audacity.sourceforge.net/ and by installing it, it goes pretty much as any other program.

I have a VIA Dreambass 24 bit USB soundcard and a microphone attached to it. First plug it in so drivers get installed and then start audacity.
Select the VIA as your microphone and mono as your input mode if you do silencer measurements. If you do action noise measures with earphones
then select stereo as you’ll be recording both muzzle blast and action noise in sync.

Then it’s time to set the recording level. Get your gun ready, press rec button, fire a shot (empty shot recommended) and press stop.
See what kind of noise peaks you recorded, if there’s red color in that noise track you need to tune the mic sensitivity down.
Repeat until you get good reading with no red color in the line.

Now it’s time to record some shots. I usually set the laptop with microphone some 5 meters in front of the gun in my garage. Fire 5 shots while
recording and then cut off the parts of the recording that are not actual shots. Then in the analysis menu (I need to translate these as my
audacity installed itself in local language) select draw spectrum. This shows the decibel level for each frequency. You can play with settings
but I’ve found the default to be OK. Then export the data to a file and import that file to an excel sheet. I only use data up to 20 kHz as that’s
the upper limit of human hearing range. In excel you can then draw those nice graphs and thus easily compare one gun to another.

If you do the action noise recordings, use regular cheap earphones with those small button type speakers. Set the recording to stereo and press
one speaker against the breech while holding another close to muzzle. Fire a blast and again play with microphone sensitivity until you get it right.
You should now have two tracks showing the firing events and muzzle blast. When you zoom in you can see how the hammer starts moving, hits the
valve, air starts moving to the barrel and blast out, hammer bounces back and probably hits the valve a second time causing another blast of air to
come out etc. Since there’s time track in those recording you can measure how long it takes for things to happen and try different things for reducing
lock time or hammer bounce etc.

All in all audacity is a very useful tool to have if you are serious about tuning your airguns.

Slainte, Riku

I’ve been using audacity for two purposes, to record the hammer/action noise with poor microphones and to record the silencer noise levels with good microphones. It works for both. The hammer/action noise lets you see the hammer bounce and you can then do the mods to get rid of it. With good mic you can record the noise levels of different silencers and silencer mods and compare them to each other to let you know if certain mod improved the noise level or not. What I did for noise level recording was to fire 5 shots, cut out the irrelevant times in between and then did the spectrum analysis to get those graphs. As you can move the decibel peak to different frequency areas by modding this is a great way to see what the real effects are and where in the frequency area the peak decibel level occurs.

Unfortunately I do not have MRod at my disposal, otherwise I’d show you what the “mousefart” in US is compared to a typical 12 fpe gun with good silencer as used in UK (less than US mice can fart). As a matter of fact I do have some mice at my backyard but I’ve heard them fart, either they are on a good diet or the fart can not be heard.

Edit: Forgot to say, the action noise recording also shows you the lock time and when pellet leaves the barrel if you are interested in those things.

I think just about any mic will work as long as you use the same one for all the testing.

RKR was pushing the idea of using the crappiest one available in order to reduce the hammer slap interference. I think that has merit as well as getting a good one that will measure the slap since it is part of the ‘noise’ involved in firing.

Start with what is available and see what you get for data, then if needed buy accordingly… 😉

Of course this will lead to buying more airguns to test. No way around it now!

This just popped up on the Yello…

http://www.network54.com/Forum/79537/thread/1380912828/Audacity+Sound+Program+Revisited

I would forego the meter and get a couple of mics (a good one and a crappy one) and use Audacity to compare the sounds. If you set up the mic the same each time (typically 3′ from the source in a straight line, pointed 90 degrees to the sounds projected centerline or the pellet path and three feet to the side, three feet away from the pellet path) you can compare the sound profiles of the various shots.

In the Hoot Cricket/Edgun quieting post the guy with the cool graphs was using Audacity. Having the profile is more important than knowing the level in the long run really.

Here is one of “rkr”s graphs…