Regarding noise levels of SD shootings..

[triggertime]

Southern Raider,

You said:

"dB is a logrithmic measurement much as the Richter scale is for earthquakes. It's not linear. Each 10dB represent 10 times the energy hitting your ears. In other words, the roughly 8dB difference between a 357 and a 38 represents 6.3 times the energy hitting your ears."

Detention for me? In Sanow's article he notes that he used a Quest Model 215 Sound Level Meter set to the linear or unfiltered scale.

You've stated that dB is a logrithmic measurement that is not linear and that each 10dB increment represents 10 times the energy hitting your ears.

From what I've cited from the example in Sanow's article, the difference between 117dB and 131dB is 14dB. How is 14dB a 25 times increase if you've stated that 10db only represents a 10 times increase?

Instead of sending me to detention for supposedly not paying attention, perhaps you should be sent there instead for being contradictory in your explanations.

Here's an idea, take Sanow with you so both of you can play a little paper football to pass the time.

 

[Southern Raider]

TriggerTime,
I'm sorry, but I cannot change the engineering analysis and math behind all this. It is widely accepted and confirmed. I also fail to see where I have been contradictory in my explanation. Each 10dB increase is a 10 times increase in power. (10dB is 10 times, 20dB is 100 times) What is perhaps confusing you is that a linear progression in decibels represents a geometric progression in power levels. In other words, addition in a logrithmic scale is the same as multiplying in corresponding linear scale.

I don't know what the Quest Model 215 Sound Level Meter set linear or unfiltered scale entails, but decibel measurements are logrithmic. That is how they are defined.

If you want the answer as to why a 14dB increase represents a 25 times increase in power, look at my previous post for the math, or

power increase = 10 raised to the (dB increase / 10) power

For the example, 10 raised to the 1.4 power = 25. Get a calculator and check it yourself. You can also check that 10 raised to the 1 power is 10 and 10 raised to the 2 power is 100. (i.e. 10dB is 10 times greater and 20dB is 100 times greater)

Or we can do it as you seem comfortable. The first 10dB represents 10 times the power. Four more dB represent approx. 2.5 times the power. Since adding algorithms represents multiplication in the scalar domain, 10 * 2.5 = 25.

Don't forget to clear the erasers in detention hall...

 

[Double Naught Spy]

Y'all can argue all the physics semantics all you want. Most of that is out of my league. No matter how you do the math, there is not any normal caliber and unsilenced firearm that is auditorily safe to fire indoors w/o hearing protection such as might be done in a self defense shooting.

And JohnKSa and jc2 are absolutely right about auditory exclusion. Just because you didn't hear the shot (mentally) does not mean that you didn't suffer the effects of the over pressure. This is a mechanical issue. Once again, take a look at the like I posted above. Included there are pictures of the mechanical damage that can result from experiencing sounds that are too loud.

Also once again, the loudness of the gun or caliber is not the only salient issue here. There is a definite directional aspect as well. In shooting outside with little reflected sound, shooting my AR is not unpleasant at all as I am directly behind the muzzle that is pointed away from me. Five feet to my left or right and the experience is not so pleasant for a person in those locations. Being slightly down range and a few feet to either side is a lot worse. Of course, some guns project sound more directionally than others.

 

[bountyhunter]

CONFUSION

"Detention for me? In Sanow's article he notes that he used a Quest Model 215 Sound Level Meter set to the linear or unfiltered scale.

You've stated that dB is a logrithmic measurement that is not linear and that each 10dB increment represents 10 times the energy hitting your ears. "

dB's are definitely logarithmic excatly as described in the threads. The "linear" herring thrown in is also correct, but has nothing to do with dB's:

All acoustic meters have different "scales" which adjust how the microphone's frequency response is dialed in to the meter. The "linear" scale (commonly called the "C weight") means all frequencies are given equal loudness so the response of the input stage is linear (flat) with frequency, hence the statement it is the "unfiltered" scale.

The human ear's frequency responce is extremely non-linear, and drops off tremnedously at lower frequencies. Most acoustic meters ahve another scale that mimics the ear's frequency response (the "A weighted") scale, which is actually more indicative of how loud a sound will hear to a person. The sound input to the meter is fed through filters to approximate the ear's characteristics.

 

[bountyhunter]

Genuine Truth Here

"Also once again, the loudness of the gun or caliber is not the only salient issue here. There is a definite directional aspect as well. In shooting outside with little reflected sound, shooting my AR is not unpleasant at all as I am directly behind the muzzle that is pointed away from me. "

YES! And, at an indor range, the sucker in the lane next to the magnum is getting blasted worse than the shooter because there is a bit of a null (dropoff) directly behind the muzzle. Still loud, not as loud as the poor schmuck in the next lane hears.

 

[JohnKSa]

the sucker in the lane next to the magnum is getting blasted worse than the shooter because there is a bit of a null (dropoff) directly behind the muzzle.

True--unfortunately the null is small (spatially, that is.) So small that shooters tend to lose their hearing in their weak-side ear first because it is farther off the bore axis than the strong-side ear.

 

[cratz2]

From listening to car stereos, 10dB is a big damn difference! 120 dB is a loud but comfortable listening level, 130 dB you are going to have a hard time talking over it, 140 dB and the guy one block down can hear the bass.

I also know the difference between shooting 124 Gr +P out of my Kahr with a 3.5" barrel is a world of difference louder than shooting 230 Gr SP or +P out of a 5" 45ACP. Now I'm sure a lot of that has to do with supersonic vs. subsonic and being behind the gun (which is hopefully where you will be) may mean there's a bigger difference in actual shooting.

Inside the house, I have no clue but just shooting outside, the 45ACP is much more quiet than the 9mm.