MIL-STD-1474D
Explaination of noise level measurements and its importance
The MIL-STD-1474D standard and how to properly perform noise level measurements.
To measure the sound levels, or noise levels from firearms or firearms equiped with a silencer requires extensive experience and knowledge in the subject.
The typical sound, or noise from a firearm is generated from two things. A sudden release of hot, high pressure propelling gases in the bore, and the sound of the bullet in flight (Sonic boom).
The noise from the sonic boom is generated outside of a firearm and/or outside of a firearm equiped with a silencer, and cannot be addressed by the silencer.
However, the noise generated from the release of the high pressure gases is the only noise a silencer can reduce by slowing down and reducing the pressure of the gases before they are released into the atmosphere (surrounding air).
The current standard or the commonly used standard for measuring noise levels from firearms is: MIL-STD-1474D.
MIL-STD-1474D specifies the exact procedure and how to perform the test, including sound level meter type, microphone positions, operators positions, surrondings, etc.
Stalon AB utilizes the MIL-STD-1474D on all noise level measurements with an exact setup according to the standard. This is a very important procedure for Stalon to be able to present a precise and accurate result of noise reduction of the Stalon silencers.
MIL-STD-1474D specifies two options of positioning the noise meter (microphone), or rather one(1) with an option to add a reference position at the "shooters ear".
The first, and the most important position of the noise meter is placed at 90 degree angle, 100cm left from the bore exit of the silencer, both the silencer and the noise meter should be 160cm above short-cut grass. This position provides the actual noise reduction of the silencer. The "shooters ear" postion is a reference position to measure the noise exposure for the user, or "shooter". The noise meter should be placed under the same cirumstances as the first one, but now at the location of the "shooters ear" and 15cm from the bore axis (line of sight).
The "shooters ear" position does not take into account how long/short the barrel and/or silencer are, and will result in a irregular result depending on lenght of the firearm and the length of the silencer. The further away the noise meter are from the source of noise, the lower the noise levels are. The "shooters ear" position is with other words not an accurate way of measuring a the noise reduction of a silencer, but could be used as a reference for the user.
All Stalon silencers are tested and measured according to MIL-STD-1474D and at 90 degree angle, 100cm left from the bore exit of the silencer. The quality and regularity of all our noise level measurements are therefore 100% true.
