Is hearing protection cumulative?

[scythefwd]

I already have a set of plugs that do 26 (claimed db) sound reduction. I bet they are even more than that because I cannot hear at all with them in (my garand is very comfortable to shoot, better than over the ear protection which is rated at something like 21 db reduction by more than a long shot). I can't hear the subsonic .22lr stuff I shoot. Unless my hearing has just gone to hell in the last 4 years (my last hearing test was in 06 when I ets'd and I was told it showed no hearing loss or impairment) I would like to keep it as it is.

I was considering getting a set of over the ear muffs to use in conjunction with my in the ear plugs. Will the total reduction be the sum of the two ratings or will it be something different? I know db is measured in a logarithmic scale (every 3 db doubles volume), so I'm not sure of the ratings should be summed or if the protection level would be figured out differently.

This is for extended shooting sessions, 2-3 hours shooting loud(ish) stuff like .308 win.

 

[vtbluegrass]

I couldn't say for sure if the reduction will be cumulative but it will reduce more sound by adding muffs to plugs. I only double up when shooting magnum revolver in most cases but it definitely dulls the roar even more.

 

[blutarsky]

short answer is "no, they are not cumulative" -- if you have muffs rated at 21 and plugs rated at 30, you do not get a total rating of 51... it might be more like 35. you get an advantage, but it's a modest one.

when shooting indoors, especially, i'd recommend doubling up on muffs and plugs... i wear some good plugs and then use electronic muffs over top with the volume turned up, that way i get a slightly better ability to hear voices if needed. it works quite well, actually.

 

[Ed Ames]

Absolutely they are cumulative.

Decibels being what they are, 40+40 = 43. (Logarithms are like that.)

 

[scythefwd]

I don't shoot indoors, so it might not be worth the extra money after all but thanks. Ed, that was so obvious that I looked right over it... hehehehe. Definitely a DUH moment. Thanks, I needed the laugh.

 

[Double Naught Spy]

short answer is "no, they are not cumulative" -- if you have muffs rated at 21 and plugs rated at 30, you do not get a total rating of 51... it might be more like 35. you get an advantage, but it's a modest one.

Actually, the hearing protection is cumulative. In doubling up, a 150 db sound passing through muffs with a 25 nrr result in 125 dbs that are then met by the plugs. If the plugs are 30 nrr, then only 95 db passes through the plugs.

However, a goodly amount of that nrr benefit is lost due to bone conduction. Muffs and plugs mainly protect against sounds entering through external auditory meatus.

 

[harmonic]

Some info I got off the net.

The way you actually hear something is that ganglia (small hairs in your inner ear) vibrate from the result of moving air hitting them, transmitting a message to your brain. When the ganglion are assaulted by an extremely loud stimulus (e.g. crash, jet engine, gun shot), they get "pushed down" a little. They never "stand back up" to their full extension. People lose their hearing as they get older as a result of continued assaults upon the ganglion, pushing them down more and more each time. This results in hearing loss, the ganglion are no longer able to effectively transmit a given message. The loss of frequency (pitch) recognition can be segments of the full spectrum, all hertz between low and high.

Facts on noise levels:
1. Decibels measure sound pressure and are logarithmic. That means that only a 3db increase almost doubles sound pressure, a 6db increase quadruples sound pressure, etc.
2. Gradual hearing loss may occur after prolonged exposure to 90 decibels or above.
3. Exposure to 100 decibels for more than 15 minutes can cause hearing loss.
4. Exposure to 110 decibels for more than a minute can cause permanent hearing loss.
5. At 140 dBA noise causes immediate injury to almost any unprotected ear.
6. There is also the more extreme ‘acoustic trauma’, which is an immediate loss of hearing after a sudden, exceptionally loud noise such as an explosion.

Comparative noise levels and length of time exposed to cause permanent damage
Jet engine taking off 140 dB Instant damage
Thunder/Ambulance siren 119 dB 3 minutes
Hammer drill 113 dB 15 minutes
Chain saw/Earphones/Concert 110 dB 30 minutes
Bull Dozer 105 dB 1 hour
Tractor/Power tools 96 dB 4 hour
Hairdryer/lawnmower 90 dB 8 hours


Noise levels of firearms:
.22 caliber rifle 130dB
.223, 55GR. Commercial load 18" barrel 155.5dB
.243 in 22" barrel 155.9dB
.30-30 in 20" barrel 156.0dB.
7mm Magnum in 20" barrel 157.5dB.
.308 in 24" barrel 156.2dB.
.30-06 in 24" barrel 158.5dB. In 18" barrel 163.2dB.
.375 18" barrel with muzzle brake 170 dB.
.410 Bore 28" barrel 150dB. 26" barrel 150.25dB. 18" barrel 156.30dB.
20 Gauge 28" barrel 152.50dB. 22" barrel 154.75dB.
12 Gauge 28" barrel 151.50dB. 26" barrel 156.10dB. 18" barrel 161.50dB.
.25 ACP 155.0 dB.
.32 LONG 152.4 dB.
.32 ACP 153.5 dB.
.380 157.7 dB.
9mm 159.8 dB.
.38 S&W 153.5 dB.
.38 Spl 156.3 dB.
.357 Magnum 164.3 dB.
.41 Magnum 163.2 dB.
.44 Spl 155.9 dB.
.45 ACP 157.0 dB.
.45 COLT 154.7 dB.

Properly fitted earplugs or muffs reduce noise 15 to 30 dB. The better earplugs and muffs are approximately equal in sound reductions, although earplugs are better for low frequency noise and earmuffs for high frequency noise.

Using muffs and plugs together: Take the higher of the two and add 5 dB. 30 plug with 20 muff gives an effective NRR of 35.

If you are shooting by yourself, with plugs and muffs on, you get to shoot up to a thousand rounds without damage (louder ammo/gun and the allowable drops by a factor of 5). Shoot with other people and you have to add all the rounds shot cumulatively (10 people shoot 100 rounds and everybody's done for the day; toss a handcannon or 30 cal rifle in and you're back down to 200 rounds cumulative). If you shoot on an indoor range then all the rounds fired while you are on the range go into your total. So you can see that it doesn't take very long on a range to have a thousand rounds popped off around you.

Don't forget about bone conduction of concusive sound waves. The mastoid bone will transmit the sound vibrations directly to you inner ear where the cochela and the hearing nerves resides. Constant exposure to this kind of concusive sound waves, ie: 50 BMG, industrial heavey machinery, will result in the degradation of your hearing quality. Even with ear muffs, bone conduction is a big factor in hearing.

 

[Oro]

short answer is "no, they are not cumulative"

Senator John Blutarsky is on the right track, but the problem is the definition of "cumulative" - is it strict (e.g., 2+2=4), or just soft, (2+2= more than 2 but less than 4). Let's not get bogged down in technical mathematical definitions of "cumulative" and "additive."

Hearing protection IS additive/cumulative in the broad sense - more helps. Outer muffs will greatly dampen and distort sound waves hitting the inner ear protection, which make their job easier. Keep in mind the rating you see for any individual component is the maximum effective level it will provide, not the absolute level it provides in all situations. Furthermore, in my experience most people do not insert/install soft canal plugs effectively enough, but that's another issue.

I shoot with soft ear foam plugs under muffs when indoors. Keep in mind, shooting environment matters, too. Indoor ranges provide nice baffles (ceilings, hard floors, and stall walls) that re-direct sound waves back at you. Outdoors, the sound travels away from the barrel linearly without redirection back at you. Outdoors, I'll shoot with only one layer of protection - just muffs or plugs. I know that while my gun is generating the same noise level, my ears are getting less of a battering from it. But indoors, using both is better. Like Bluto said.

Another thing to know is that, unlike most cells in the body, the hair cells of the auditory apparatus do not regenerate. Dead is dead. it's not like your skin or even bone or muscle that if damaged, it can heal and repair. The auditory cells are among the very few cells that do not get replaced when they die. So taking very great care with your hearing is very important.

 

[scythefwd]

Oro - I mean strictly in this case. I agree that they are additive as you put it. I also agree most people don't insert their incanal plugs well enough. I don't use the soft foam ones, I use the ones that have 3 "baffles" for a lack of a better word. I know the first is fully engaged in my canal, and I'm pretty sure the second one is in contact with the opening. They are the best by far I have ever put on, excluding the set I had in the military, which I lost.

 

[Oro]

For long shooting session like you described, I would definitely use double protection, even outdoors.

The hair cells (yeah, that's actually the technical name!) in the ear don't "recover" fast, either. So if you shoot some rapid groups, you'll do damage out of proportion to what slow fire will do at the same decibel level.

It's kinda complicated, but focus on this: to do the weird things that auditory cells do, they work almost opposite the way other body cells do - the type of chemical interaction with the blood stream, etc. This is what makes them really vulnerable to damage and unable to heal. Another thing to keep in mind is they (the hearing cells) evolved to work well in an environment when all they were expected to survive against at the upper range was the roar of a lion or such. 100db or more stuff is way outside what our hearing apparati are designed to deal with. Modern noises like machinery, jet engines, gun shots, rock concerts, are pure death to our hearing sense. Protect it at all costs. I thank god now I was young when I saw The Who, The Stones, etc. And especially Dire Straights. They where one of the loudest groups to ever tour outside those metal idiots that try intentionally to induce hearing loss.

I got manic about this as a kid. My dad suffered hearing loss from military training. He made us use ear protection near a gun when I was but wee. Later in life, I started using foam plugs for study - even a library's noises distracted me. I double covered whenever I shot. When I went for my 2nd military commissioning physical (at age 32) the tester was shocked at my hearing ability - I tested them down to the lowest levels of their scale. For my age group I was in the top 1/2%.

Two years ago, I was out horseback riding and was on a hill, felt an auditory "pop." My friends head nothing. We went home and found out on the evening news that a propane tanker had exploded - 50 miles away. At the minute I turned to them and said "did you feel that?".

I am not boasting I have some supernatural spidy-hearing. All I've done is protect mine my whole life and it is now as good as a child's. So I highly recommend you double up.

Baffle plugs like you described work well. They provide multiple redundancy, but they tend to be harsh on the ear canal and irritate it. Soft foam plugs work just as well if a person learns to compress them fully before insertion, insert them deep enough, and allow them to expand fully before relying upon them. They also need to be replaced often. Most pharmacies sell bulk packs of these for a few dollars, and I think they are great for anyone who wants to protect their hearing.

Sorry to rant.

 

[scythefwd]

Wha??? I rarely do rapid fire... I can't afford it

 

[Oro]

Wha??? I rarely do rapid fire... I can't afford it

He he, I "hear" that. My personal goal is to make enough money to afford a 1928a1 Thompson. I already have Dillon set to reload .45acp, but that puppy is going to be expensive to feed...

 

[scythefwd]

I know what you mean by irritate. My ears always feel like they need cleaned after wearing them and they itch for a little bit after wearing them, but they are the best protection I have ever put in there. I haven't found anything that comes near them so far, and I have tried different muffs as well as the roll up types. The next best are the muffs for me. The roll up and shove in types never seal well for very long. I get a good seal for about 10-20 minutes, then they start working themselves out. Almost as good as the baffle types.

 

[Oro]

The roll up and shove in types never seal well for very long. I get a good seal for about 10-20 minutes, then they start working themselves out

The trick with these is that you roll them up until they are pencil lead thin. Then push them in deep. Keep your finger on them on the outside so they don't creep out as they expand. This is kind of 'high maintenance' installation, but once you do that they are wedded to the canal and will not creep out or allow noise in.

Like I said, I am an ear-noise nazi about protection. The soft ones are really my favorite, but they require a bit of technique and skill to get right. I sleep with them at night, actually. I sleep like a baby with them in. Or, at least a baby who dreams about unrestricted Wild Weasel strikes against high-value SAM site targets in North Vietnam, followed by LGB and BUFF strikes. Dreaming of doing "Rolling Thunder" right is my nightly go-to-sleep fantasy. Color me weird. I love to nod off thinking of that HARM or Shrike hitting home...

 

[hso]

blutarsky and Ed Ames are both correct.

The benefits of muffs over plugs are cumulative, but because Sound Pressure Level and Noise Reduction Rating are logarithmic you only add 3 or 5 dB to the protection of your highest NRR in use. 30+20= NRR 35 protection not 50. That means that a 150 dB AR shot would be reduced by NRR 30 plugs and NRR 20 muffs to ~ 115 dB. I use "approximately" because there are arguments in the industrial hygiene community over whether the NRR is a good measure of protection, but for now it's what we have for a commonly used unit.

So, "Yes" the protection is cumulative, but you only add ~5 to the NRR of the higher of the two properly worn type of hearing protection you're using (improper use reduces the protection greatly).

You should not allow yourself to be exposed to any noise level over 140 dB, even momentarily, without hearing protection.

 

[scythefwd]

Oro- that is what I do. They always work their way out of my right ear... Haven't the slightest clue why.

HSO - I don't ever go without protection. I gave my dad a bit of hell when he took my wife out to shoot a .22lr handgun and a .32 acp without them. I have gone without in the past, and I find it not to my taste.

 

[hso]

scythefwd,

What most folks may not know is that not all ear canals are the same. Some are larger than others while some are smaller. Ear plugs are normally made to fit that big "average" group in the middle. You may have a larger than normal ear canal or even straighter than normal ear canal (the little turn in the ear canal helps keep the plug in

). A few manufacturers make larger sized foamies for folks with larger ear canals, but your best solution may be to get a custom molded set so that the right ear plug won't work it's way out.

As to not wearing plugs and muffs, I didn't start out being retentive about it. I have continuous tinnitus (ringing) that's probably due to early shooting experiences and measurable hearing loss. I'm now very protective of the hearing that I have left.

 

[scythefwd]

I'm using plunger type plugs (they have baffles) that fit really well and block out a lot of noise. I'm a bit retentive about it as well. I carry a pair with me in my shooting stuff, plus a set of spares for anyone who might be around.

 

[hso]

See if you can find larger and smaller sizes and try them in that ear to find out if it's a question of ear canal size.

 

[mustang_steve]

Decibels (db) is logarithmic...every 10dB is a doubling in percieved loudness (sound pressure level (SPL)).

That said, there is sound that enters your ear canal directly, and in the case of loud sounds, vibration induced noise (head vibrations, etc).

Ear plugs and earmuffs reduce direct noise. Ear plugs may reduce vibrational noise, but have little effect on it. With the SPL of a firearm, there is noticable vibrational noise.

That said....if you have two 30db reduction devices, you will see about 33db overall reduction. Keep in mind a 30db reduction is a near 75% reduction in percieved loudness, this is due to the logarithmic nature of the rating. 140db is twice as "loud" as 130db, and 130 is twice as "loud" as 120, etc.

Does this help any?

 

[Tilos]

Low Tech

A lot of tech stuff answers....

So what's the downside to doubling up???
Some low tech tests:
Put on some muffs (in a store) and tap the shell with a finger nail and experience sound transfer.

After one shot with muffs only, with the muffs touching a rifle stock, is all you'll need to stop shooting and put in the plugs and adjust those muffs.

Double Up, what's the down side??

Ask an experienced shooter: tap him on the shoulder, get real close and holler in his ear.

$20 for muffs, $0.25 for plugs or a $1000 hearing aid....your call.

YMMV
Just sayin'
Tilos

 

[Mal H]

Decibels (db) is logarithmic...every 10dB is a doubling in percieved loudness (sound pressure level (SPL)).

Not quite true. As mentioned above a doubling of sound pressure level is about a 3 dB rise in SPL. A 10 dB difference would be a 10 fold increase in the SPL (not 3 1/3 times as it would seem to be if using an arithmetic scale). The remainder of your post needs to be adjusted accordingly.


A trivia quiz for everyone - What is the loudest thing on earth as measured in its dB output? (Hint - it's an animal.)

 

[divemedic]

Just so you all know, there is a limit to the cumulative effect of hearing protection. The muffs and plugs only prevent the pressure waves in the air. Sound is also conducted through the soles of your feet and through the bones of your head. For that reason, the best hearing protection will only reduce perceived noise by a maximum of 35 dB.

The Blue Whale is what you are talking about, but the loudest sound ever recorded was the Tunguska meteor blast June 30, 1908. The explosion was most likely caused by the air burst of a large meteoroid or comet fragment at an altitude of 5 to 10 kilometers (3–6 mi) above Earth’s surface. It was measured with the similar impact of a 1000-Mega-ton bomb with a decibel rating 300-315.

For comparison, Krakatoa at 180dB is about 13x as loud as a jet engine from 100 ft, or as loud as a rifle shot at point blank range. People 2,200 miles away in Perth, Australia could clearly hear the eruption immediately after the explosion.

 

[Mal H]

The Blue Whale is what you are talking about ...

Nope, that's not it. Blue whales, and in fact most whales are exceptionally loud, but the animal I'm talking about is even louder dB wise.

People 2,200 miles away in Perth, Australia could clearly hear the eruption immediately after the explosion.

I think you're talking about the eruption of Krakatoa, not the Tunguska event.

 

[CoRoMo]

[strike]Howler Monkeys[/strike]

Snapping shrimp. Google-Fu got me there!!