This article was written by me and originally appeared in Safezone Magazine.

A question I often see on the forums is "How loud is an airsoft pistol?".

A flip side to that is "Which is the quietest airsoft pistol", so I thought I'd try and measure it.

I bought a basic sound meter from eBay. It is analogue (wavy arm, to you and me!) and doesn't have the ability to record maximum levels, so there is degree of inaccuracy in my tests caused by

a) the arm moving continuously
and
b) me having to judge where the needle reaches as a peak.

Fortunately, the purpose here is to assess the comparative loudness of different pistols and the overall level of sound compared to everything else.

Now, if you're like me, you probably didn't have a clue what a Decibel was until you started reading this, so I tracked down a rather handy little table (Source: National Institute of Deafness and Other Communication Disorders), which lists common sources of sound and how loud they are.

Decibels are measured on a logarithmic scale, so a rise of 10 dB in sound level corresponds approximately to a doubling of subjective loudness. That is, a sound of 85 dB is twice as loud as a sound of 75 dB which is twice as loud as a sound of 65 dB and so on. That is, the sound of 85 dB is 400% times the loudness of a sound of 65 dB.

If you are really interested, there is lots more information at : http://www.rtagroup.com.au/wizard/definition_acoustics.html and http://www.e-2-s.com/kb-3.htm.

I used the calibration button to set my meter and then monitored a quiet room - Sure enough, it comes in around 40dB.

So, knowing the meter was reasonably accurate, I devised a way of testing airsoft pistols.

I decided to fire 5 bbs from each gun into a soft material (to eliminate the sound of the BBs hitting) and to measure the sound of each gun a set distance (10 CM/4 inches) away from the muzzle (to try and give a balance between GBBs, where the slide causes a lot of noise, and NBBs).
As I fired each BB, I observed the highest point that the needle reaches and averaged my observations out over the 5 shots. I found that I was able to be accurate in determining the peak dB to within one gradient on the gauge, which is 2 dB.

So, onto the results...

First gun tested was a springer, my TM S&W PC356.

The sound is very sharp and plasticky and most seems to come from the spring releasing in the frame. The average was 84dB.

Next up was a NBB, my Maruzen S&W 4506. This has a very abrupt, 'pup' sound to it and recorded 88dB.

Finally, I tested a GBB, my KSC MK23 SOCOM. This is an especially interesting gun as I have a foam filled silencer for it (the TM one from the NBB Mk23) and I was interested in the actual level of sound suppression that accounted for. The sound is best described as a hollow 'pop', but a lot of metallic sound is mixed in.

Most of the sound of a GBB emanates from the slide moving and it was no surprise that it was the noisiest at 94dB.

What I did find impressive (and giving lie to the belief that the sound is all in slide, perhaps) was that this dropped to a mere 86dB with the silencer fitted (a drop of almost 50%). Imagine that on the already quiet TM NBB Mk23 and you have an idea why it is widely acclaimed as one of the quietest airsoft guns around.

Subsequently, I tested another 6 guns and recorded almost identical results for each type of gun (NBB or GBB). This would suggest that all guns of a particular type are pretty much even on volume, although different guns have a different tone to their sound, which makes some seem louder than others.

I will apply the sound test to all my guns in future to give an idea of the relative 'noisiness' of each gun.