Originally Posted by SystemaEncephale
What I mean by that is, I have a G21 and a G17 and I prefer the 17 for home defense for 2 reasons. First being it's capacity, second being it isn't nearly as loud as a .45.
I don't doubt that in your experience the noise generated by the G21 45ACP seems louder than the G17 9mm.
The published data I've seen is counter-intuitive:
Table 3. CENTERFIRE PISTOL DATA⁽¹⁾
.32 LONG 152.4 dB
.32 ACP 153.5 dB
.38 S&W 153.5 dB
.45 COLT 154.7 dB
.25 ACP 155.0 dB
.44 Spl 155.9 dB
.38 Spl 156.3 dB
.45 ACP 157.0 dB
.380 157.7 dB
9mm 159.8 dB
.41 Magnum 163.2 dB
.357 Magnum 164.3 dB
1. Gunfire Sound Levels provided by earinc.com from data originally published by Dr. Krammer, Ph.D., Ball State University, Muncie, Indiana
Keep in mind the dB scale is logarithmic, not linear. For example, an increase of 3 dB is a doubling of the power or intensity of the sound, and an increase of 10 dB means the sound intensity is increased by a factor of 10 times which would be perceived by the human ear to be roughly twice as loud in volume.
The specific pistols used by Dr. Krammer for the results above aren't included in the reference. I haven't seen data specific to the G17 and G21. SilencerCo recorded 161.4 dB A-Weighted Average for a Springfield 1911 45ACP indoors (see http://www.youtube.com/watch?v=Vt4AJM75dIU
140 dB noise and above can cause immediate injury to almost any unprotected ear. Perceived auditory muting does occur
under the stress of gunfighting (see study by Dr. Alexis Artwohl) but that doesn't lessen the risk of permanent hearing damage after repeated exposure.
There is a very interesting article with some pertinent information on this topic:
Exposure to Recreational/Occupational Shooting Range Noise vs. Industrial Impulsive Noise
I believe the general conclusion about the relative danger of exposure to impulsive noise of a firearm discharged indoors during home defense is summed up in a quote from the article:
"A single unprotected exposure to loud gunfire can result in a temporary hearing loss. However, repeated exposure to impulsive firearm noise can result in permanent noise-induced hearing loss."