Thread: Suppressor effectiveness - Think about this!

Originally Posted by gonetropo

ok seems my last post disappeared into nothingness ( no bad language etc so who knows)
dB is a log scale invented by alexander graham bell's company to pretty much talk about volume on phone lines. however a "bell unit" was way to loud so in came the decibel (1/10th of a bell). ok here it gets slightly techy.
to increase sound pressure (what you hear) increase by 10dB, to decrease what you hear by 1/2 decrease by 10dB
now subsonic loads have no penetration into the supersonic so as they silence only the muzzle "crack" the projectile itself is relatively silent. above the sound of sound although you may silence the muzzle blast the projectile will still make a supersonic wave to hear.
so to give an example a 38 revolver is 138dB, about as loud as a 747 plane at take off, but 128 dB is 1/2 as loud. 118 dB is 1/2 as loud as that again.
it also works the other way add 10dB and its what you perceive as twice as loud, still mazes me that salesmen keep telling me that double the amplifier power = double the volume. well thats what you get when you pay peanuts.
any more question feel free to pm

Emm yer a wee bit out there about the 10 dB and halfs. DB's are exponential therefore for every gain of 3dB you actually double the noise, noise is simply a wave of pressure that leads to vibration, or for every loss of 3dB you half the noise. It's also not about perceived loudness it is an actual measurement.
Thats why at 85dB you can be exposed to that level for 8 hours without hearing protection before damage starts whereas at 89dB you only have 4 hours and for every 3dB gain you half the time you can be exposed before you start requiring hearing prtection.
Most noise testing covers the following:
Lmax- this is the maximum decibel level reported. In the workplace it needs to be below 140dB to meet NZ requirements.
Laeq- this is the average decibel reported.
There is also a reading noted as Lpeak which is a pressure reading which can also destroy hearing without the person realising. Humans are not able to perceive certain frequencies of noise such as the high frequency 20,000hz that a bat can however there is still a pressure form there that can be transmitted through the ear and that is what Lpeak is measuring.
If you are getting Lmax and Lpeak above 140dB you really should be looking at specialist octave band testing to let you know what frequencies you are being exposed to and make a suitable plan from there.

I have always meant to take the meter down to the range and see what is going on but not got enough time.