Silencers and physics

[ranb]

At times I discuss silencers and their effectiveness online with others. It is usually to describe how well they work and their limitations. After searching on the net and trying to educate myself, I have found several means of putting silencer performance on paper. Intensity, sound pressure level (SPL) and loudness.

Intensity (dB) = 10log(X2/X1)
SPL (dB) = 20log(X2/X1)
Loudness (dB) = 33.22log(X2/X1)

This makes a 10 dB change in intensity equal to a ten times change in sound energy, a 10 dB change in SPL equal to a three times change in sound energy and a 10 dB change in loudness equal to a two times change in sound energy. A 30 dB change in intensity would be 1000 times, 30 dB SPL 32 times and 30 dB loudness 8 times more or less noisy.

So while I can tell a person that if a silencer lowers noise by 30 decibels is 1000 times less noise energy, it is only 8 times less noisy to the ear. The loudness is of course subjective and differs between silencers on how they change frequency and how well people hear.

Right? Wrong? Suggestions? Thanks.

Ranb

[continuity]

Interesting stuff.

Thoughts are that the practical element to the "equation" is the perceived loudness of the shot to the human ear. Much like the human eye is more or less optically receptive to different light waves, even though those light waves (i.e. white, blue, red, infrared, etc.) may have the same intensity.

That is if one is only interested in the human aural element of suppression. A field agent may also be interested in the pressure wave and/or other energies that can be detected by locating devices.

It seems also that the total energy of the sound signature is a sum of the different elements (not an epiphany by any means). Since enery can neither be created nor destroyed (only redefined), one element may be suppressed more effectively but only at the expense of the other(s).

Just my 2cents worth.

[boulderchild]

thats pretty slick!!! I'm going to play with this when I get some time.

[LavaRed]

What are X2 and X1?

[CKOD]

What are X2 and X1?

Your before and after numbers, you'd feed PSI, KPA, Bar, into there, and it'd spit out the db difference. For measurements like the dBA/dBC measurements that decibel meters use, 0dB is set at a standardized value for the lower limit of human hearing.
http://en.wikipedia.org/wiki/Sound_pressure

it starts to get messy with dba and dbc and other weighted scales because different frequencies affect the rating more then others.

[LavaRed]

What are X2 and X1?

Your before and after numbers, you'd feed PSI, KPA, Bar, into there, and it'd spit out the db difference. For measurements like the dBA/dBC measurements that decibel meters use, 0dB is set at a standardized value for the lower limit of human hearing.
http://en.wikipedia.org/wiki/Sound_pressure

it starts to get messy with dba and dbc and other weighted scales because different frequencies affect the rating more then others.

Thank you

[saunderscc]

I seem to recall that a decibel is also the smallest increment of sound where human hearing can perceive a change in "volume."

[seattlite]

Newbie here with his first every approved Form 4.

Now that I got my first suppressor, I'm looking to getting a 2nd and was looking for a more technical comparison of the various suppressors. It seems like the comparative numbers that are floating out there on the manufactures' sites as well as on independent review sites are in measured blast SPL(dB) and/or in sound reduction dB.

I always wondered why audio spectrum measurements are not reported since a lower spectrum would tend to be perceived as "quieter" than a higher auidio spectrum. This report seems to conclude that both measured blast SPL and audio spectrum are important in Suppressor Specifications...very interesting read: http://www.dtic.mil/ndia/2009infantrysm ... xi8453.pdf

[renegade]

The science on this is extremely difficult, and the fact the market generally wants a simple XX dB reduction, only makes it harder.