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Discussion Starter #1
Just curious.....

My SA .45 with a five inch barrel and my XD9 SC with a three inch barrel seem to be about the same as far as how loud they sound.

I have been at the range on occasions and had guys with .44 magnums and I suppose .50 caliber guns near me that were so loud it was ridiculous. Actually would make me sort of jump.....not easy to shoot when someone next to you is discharging a cannon (at least I find it unnerving).

I fully expected my (new as of last Sat.) .45 to also be substantially louder than the 9mm. But they seem to be about the same. When I switch back and forth, the loudness of the XD9 still surprises me.


Is this a factor of the shorter barrel being louder? I know some of you guys have XDs in different lengths. Are the guns with the longer barrels less loud in the same calibers?

TIA.

Peace,
D.
 

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It probably depends on the powder and hence the rate of burn and the velocity of the expanding gas. Which does depend on the barrel length along with a few other factors. Ultimately that would mean the gas pressure when the bullet exits the barrel. But I think I can make sense out of this.
 

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Delija, are you talking about sounds at an indoor range? I've never shot at an indoor range and I don't think I would want to because of the sound. Gotta be murder on the ears.
 

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My ex-wife sure had good pressure then. Her db (dat b_t_h) level was maxed out. :D Sure glad it didn't have anything to do with my barrel length. :wink:
 

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Bob Hostetter said:
The db level is the result of the pressure levels. The higher the pressure the higher the db....
But pressure levels at the muzzle not the chamber, right?
 

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Discussion Starter #7
one-eyed-fatman said:
Delija, are you talking about sounds at an indoor range? I've never shot at an indoor range and I don't think I would want to because of the sound. Gotta be murder on the ears.
Yes, my cycloptic brother. This is at an indoor range. Unfortunately we don't have many choices of where to shoot here in the land of the shooting range cartel (Palm Beach County, Fl.).

But as far as "murder on the ears"...even though it's a little late in life for me (too much rock and roll and shooting), I do use both the "in the ear" plugs and the big "earmuff" style protection simultaneously. Certainly my hearing damage was done many years ago. But it can and would get worse, so I try to preserve what hearing I have left.



Bob Hostetter said:
The db level is the result of the pressure levels. The higher the pressure the higher the db....
Yes, I understand this. I spent many years playing rock and roll (electric guitar). I have had guitar amplifiers with low wattage that had enormous sound pressures, and others with very high watt ratings that did not have that kind of sound pressure (db volume). I guess the same goes for stereos. It is a function of how much air the speakers move (and how efficiently).

Don's comment about barrel length was pretty much what I was thinking. If the barrel is longer, does the sound get dissipated by having to travel further before leaving the gun? I was never good at physics, but I'm sure someone here would know.

Although I have fired a .44 with a seven inch barrel, (maybe even longer...it was many years ago) and that extra couple of inches didn't seem to attenuate any "sound pressure" (or loudness, take your pick) at all.

Am I incorrect in believing that suppressors use length to achieve (partially) their results?

As I asked in the opening post (this thread)...I know some of you have both subcompacts, and tactical XDs...Is there a difference in how loud they seem?

Peace.
D.
 

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Delija,

When you compare the sound of the 9mm to the sound of the .45 ACP, you're talking about a high pressure cartridge, versus a low pressure cartridge. The bore diameter also has a bearing on the sound you hear, along with the difference in pressure.

The two are going to produce a different sound, which will be perceived by the brain differently. In your music background, you know that two notes at different places on the scale, produced at the same db level, will have a different effect on the receiver. The same is true in shooting. The higher pressure round, in this case the 9mm, will produce a sharper crack, for lack of a better term, than the lower pressure .45 ACP, even though the two may produce the same db level.

Another factor to consider is that most 9mm ammunition is loaded pretty near the top of it's performance envelope, so it will cycle most all handguns. The .45 is loaded to many different levels, from light target loads to fullpower defense loads and it's more common to tune a .45 for the ammunition the shooter intends to put through it. I've got two .45's set up for fullpower loads and two set up for light target loads, and there is a definite difference in the sound of the two loadings.

There are many variables to consider, and only one of them is barrel length.

Hope this helps.

Fred
 

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Suppressors just give the gas somewhere to expand other than out the front of the gun. The baffles inside let the shockwave slow down... Scream into your pillow (Which, actually, would make a nice silencer) and you'll get the same effect. :)
 

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Longer barrels appear to make less noise to the shooter for 2 reasons. 1st, the longer the barrel the further away from the shooter the sound source is (the muzzle). The differences seem small but db levels drop fairly fast especially with directional sound sources. 2nd, the longer the barrel, normally the lower the pressure of the gases at the muzzle.

Suppressors are designed to trap the sound waves and force them to bounce off of baffles.This results in a loss of sound energy (which is converted to heat, which is the reason suppressor's get hot). Length and diameter of a suppressor is a function of how much gas needs to be controlled, the pressure levels being produced, what level of suppression is being attained, and the type of baffles being used.
 

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I wish I still had my old dB meter and other test equipment, it would be fun to mess with that one. I do have audio frequency spectrum analyzer software for my laptop, but I don't think it's fast enough or accurate enough to use, but I will try it, maybe this weekend, and let you know the results.
 

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The reason why your percieve sounds as louder or not louder has much to do with how sounds are measured and also where you hear sounds.

Keep in mind that you coclea does not hear all sounds in the same area. Each frequency (there are tens of thousands) are each heard by a different "hair". You are also hearing impulse sounds instead of continuous tones. That makes a difference in percieved loudness.

When you look at the sound db SPL scale (there are many different dB scales), you can compare two sounds actual volumes by using the mathmatical equation SPL=20*Log(A/B).

Thsi means that doubling the sound pressure level (SPL) = 20*log (2) or = 6dB.

Therefore, if you have a 90dB sound, it takes twice the pressure. A person typically doesnt percieve 6dB as twice as loud.

Also, percieved loudness is based upon tone. If you generate a mutitone sound with say a simulataneous tone every 1/3 octive from 250hz to 10kHz and play it at say 90 dB, and take the same sound, but elliminate the ferquencies below 1000hz, you will percieve the full spectrum as much louder, although both are played at 90dB.

So, bottom line, you must produce MUCH more sound (air) pressure to hear a difference and some tones are percieved as louder than others.

BTW, if you take you earmuffs at say a 30db rating, you are reduing the sound pressure level that hit your ears by 29 times (or 2900%). Also wearing earplugs with them reduce sound even more, but you can't take a set of 22db earplugs add a set of 30db earmuffs and get 52db of noise reduction. Many things in sound are simply not addative.

Probably more than you need to know about sound. BTW, please don;t wear any hearing protection when you shoot. My livelyhood is based upon people having hearing damage....I am only joking about not wearing hearing protection.

-Dana
 
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