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SOUND TESTING

We've been testing silencers for about eight years and there are very
specific protocols to follow. For an in depth study of the practice, we
highly suggest Al Poulson's books "Silencer History and Performance",
volumes one and two. We were very fortunate to have Al Poulson do the
early testing on our .223 titanium silencer for some magazine articles.
We've attempted to follow in his experienced footsteps with silencer
testing here at Quicksilver.
Only two sound meters are approved for proper silencer testing, both of
which are out of production at this time. These meters are now fairly hard
to locate and quite costly. One is the B&K model 2209, the other is the
Larson Davis 800B. We've owned both models over the years and have chosen
to stay with the Larson Davis 800B as it has a digital read out instead of
an analog meter. Both meters must be equipped with a 1/4" pressure type
microphone to provide a fast enough response and to tolerate muzzle blast
from small arms. Larger microphones may bottom out and give a falsely low
reading.
These two meters are the only ones approved because they have a fast enough
rise time to catch the gun shot at its peak. More modern meters, while
plentiful and less expensive, do not have the required rise time and will
miss the peak of the gunshot, thus giving artificially low results.

Standard testing protocol is for the sound meter to be placed one meter to
the side of the muzzle, approximately 1.7 meters above ground level. Ground
should be a nonreflective surface and testing should not be performed in
proximity to any hard surfaces that may reflect sound. Although not
standard test protocol, we also secondarily test at the shooter's ear to see
what level of sound is actually reaching the shooter.
The meter should be set on A weighting. The peak pressure should be
selected to be recorded and hold selected, to hold the peak pressure on the
meter for later reading. On the B&K meter you will also have to select the
approximate range of the sound within 10 dB.
Atmospheric conditions may change the readings by one or two dB and is not
considered a significant factor. What will change the sound readings are
the length of the barrel and type of ammunition used. In short barreled
rifles you will get much higher suppressed readings because all of the
powder is not burned up in the barrel prior to the bullet exiting, thus you
have continued powder burn inside the suppressor with a louder resulting
noise.
Perceived sound can also be affected by the type of action and its location
relative to the ear. The semiautomatic action will produce a significant
amount of noise with some of the suppressor blow back coming out of the
ejection port. If this is in close proximity to the ear, it will seem much
louder. Another component is bullet flight noise. This is the most
noticeable in super sonic rounds. With an adequate suppressor you may only
hear the super sonic crack of the bullet, which will over power any muzzle
blast from the suppressed weapon. The super sonic crack is a function of
the speed of the bullet and cannot be eliminated by the suppressor.
Silencer design is an art and sound testing is just part what should be a
balanced silencer package. Durability, size, weight and accuracy are also
considerations for the elite shooter.
