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Reduced-load Loudness
#1
Subject: Reduced-Load Loudness

Posted By: ML - Registered User

Posts: 213

Posted At: (12/14/01 3:25 pm)

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You’ve touched upon an interesting topic here, and one which I’ll try to address more thoroughly in the future with yet another one of my long, boring posts. This one, though, will be (relatively) short.



Since about 1975, I’ve collected quite a file on hearing loss and other physical reactions due to exposure to loud sounds. And over the years, I’ve had several pretty thorough hearing tests myself (one of the best long ago and courtesy of your tax dollars during my OCS exam for the USMC).



Reduced-charge loadings certainly will be "quieter" (more on that definition in the subsequent posting) than full-power loads from the came cartridge.



Some numbers expressed as decibels of Sound Pressure Level (dB SPL) from some typical chamberings:



.22 Long Rifle HV, 20.5-inch barrel 137.5 dB

.30 US Carbine, 18-inch barrel 148.4 dB

.30-’06 Springfield, 22-inch barrel 158.9 dB

.375 H&H Mag., 25-inch barrel 160.0 dB



Bear in mind that this is a logarithmic scale; thus a 10-dB rise indicates roughly a doubling "loudness."



The .30 US Carbine data is useful in this particular instance, because , casting a 110-grain bullet at roughly 1700 feet per second and producing about 705 foot-pounds of energy, it’s similar to some of the mid-range .30-’06 Springfield reduced loads in the previous post. Comparing the 148.8 dB for the Carbine/reduced .30-’06 Springfield against 158.9 dB for the full-power .30-’06 Springfield, and we see a significant drop.



(Be aware, this is an extrapolation, and not an exact comparison. More reliable numbers would come from firing both full power and reduced .30-’06 Springfield loads from the same rifle with the same instrumentation. Still, it gives at least a quantifiable educated guess at what we should expect.)



Exposure to even the modest 137 dB produced by the humble .22 Long Rifle will produce hearing loss if you persist in shooting without hearing protection. Shoot more and you’ll notice it less, but that’s simply because you’re losing your hearing, not because you’re getting used to it.



What does this noise mean in the woods, though? That’s much harder to predict. I’ve seen many deer shot at and missed, and rather than spook and bolt from the noise of the shot they’ve stood still, raised their heads, and looked around. On the other hand, conventional wisdom holds that loud noises spook wildlife, and we’ve certainly all seen examples of that.



There will be no doubt, though, that lower powered cartridges, or major calibers firing reduced loads, will not be heard as distinctly or as far away as full powered versions, although they will still be quite loud.



In a previous post, I discussed the subject of sub-sonic .22 ammunition, and its influence on accuracy. A bit of that post is reproduced here:



"The speed of sound isn’t an absolute figure, but one influenced by temperature and air density. Nevertheless, a figure of about 1100 feet per second is pretty close for a temperature of about 75 degrees F at sea level.



"As a bullet passes from supersonic to subsonic (faster than the speed of sound to slower than the speed of sound) is undergoes a period of instability and for our purposes a resulting loss of accuracy."



Note that a reduced load in the 1100 fps range or only marginally higher may evidence this same behavior.



More later, although it may be well into the new year.



--ML













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Of all the things I've lost, I think I miss my mind the most.
#2
[quote name='wmerrin' post='315' date='Apr 5 2004, 09:21 PM']Subject: Reduced-Load Loudness

Posted By: ML - Registered User

Posts: 213

Posted At: (12/14/01 3:25 pm)

Reply | Edit | Del



You’ve touched upon an interesting topic here, and one which I’ll try to address more thoroughly in the future with yet another one of my long, boring posts. This one, though, will be (relatively) short.



Since about 1975, I’ve collected quite a file on hearing loss and other physical reactions due to exposure to loud sounds. And over the years, I’ve had several pretty thorough hearing tests myself (one of the best long ago and courtesy of your tax dollars during my OCS exam for the USMC).



Reduced-charge loadings certainly will be "quieter" (more on that definition in the subsequent posting) than full-power loads from the came cartridge.



Some numbers expressed as decibels of Sound Pressure Level (dB SPL) from some typical chamberings:



.22 Long Rifle HV, 20.5-inch barrel 137.5 dB

.30 US Carbine, 18-inch barrel 148.4 dB

.30-’06 Springfield, 22-inch barrel 158.9 dB

.375 H&H Mag., 25-inch barrel 160.0 dB



Bear in mind that this is a logarithmic scale; thus a 10-dB rise indicates roughly a doubling "loudness."



The .30 US Carbine data is useful in this particular instance, because , casting a 110-grain bullet at roughly 1700 feet per second and producing about 705 foot-pounds of energy, it’s similar to some of the mid-range .30-’06 Springfield reduced loads in the previous post. Comparing the 148.8 dB for the Carbine/reduced .30-’06 Springfield against 158.9 dB for the full-power .30-’06 Springfield, and we see a significant drop.



(Be aware, this is an extrapolation, and not an exact comparison. More reliable numbers would come from firing both full power and reduced .30-’06 Springfield loads from the same rifle with the same instrumentation. Still, it gives at least a quantifiable educated guess at what we should expect.)



Exposure to even the modest 137 dB produced by the humble .22 Long Rifle will produce hearing loss if you persist in shooting without hearing protection. Shoot more and you’ll notice it less, but that’s simply because you’re losing your hearing, not because you’re getting used to it.



What does this noise mean in the woods, though? That’s much harder to predict. I’ve seen many deer shot at and missed, and rather than spook and bolt from the noise of the shot they’ve stood still, raised their heads, and looked around. On the other hand, conventional wisdom holds that loud noises spook wildlife, and we’ve certainly all seen examples of that.



There will be no doubt, though, that lower powered cartridges, or major calibers firing reduced loads, will not be heard as distinctly or as far away as full powered versions, although they will still be quite loud.



In a previous post, I discussed the subject of sub-sonic .22 ammunition, and its influence on accuracy. A bit of that post is reproduced here:



"The speed of sound isn’t an absolute figure, but one influenced by temperature and air density. Nevertheless, a figure of about 1100 feet per second is pretty close for a temperature of about 75 degrees F at sea level.



"As a bullet passes from supersonic to subsonic (faster than the speed of sound to slower than the speed of sound) is undergoes a period of instability and for our purposes a resulting loss of accuracy."



Note that a reduced load in the 1100 fps range or only marginally higher may evidence this same behavior.



More later, although it may be well into the new year.



--ML













--------------------------------------------------------------------------------[/quote]



Yes! I'm another of those old time shooters who ignored the warnings when I was young. In the Army in 1951, you were considered to be a WUSS if you stuck rifle patches or something in your ears to dampen the shock to your hearing. We did a lot of shooting in Army training in those days. I'm right handed so my left ear was toward the blast when firing rifles. I really know it now and have to turn toward someone speaking from that side. Oh well, live and learn. I won't shoot a 22 now without muffs (and eye protection).


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