If I recall correctly the maximum Noise Reduction Rating (NRR) for earplugs and earmuffs is around 30db. You can combine the two for a slight increase in hearing protection but you still hit a limit because of bone vibration.
Is there PPE out there to go even further beyond this? Where would it be commonly used?
I was actually wondering about this recently and I started thinking about how loud of sounds people working on the deck of an aircraft carrier would be exposed to. I found this interesting article about improving the hearing protection for them, because it turns out even for people who actually use both forms like they are supposed to (most of the people in the jobs exposed to the loudest sounds do, it would likely still be at the pain level for them if they only wore one so they have good motivation) it still isn’t enough for a full workday of exposure.
Here’s the link: https://apps.dtic.mil/sti/pdfs/ADA455113.pdf. The exposure is something like 145-155 dB. They say a final checker will get to the safe limit in only a few takeoffs, and that assumes that they can recover in a below 84 dB environment when they aren’t working, which apparently also doesn’t happen. It seems like it isn’t really a solved problem of how to protect people being exposed to this kind of sound level.
Couple years ago, I visited a historic grand prix that featured classic F1 cars. They also had open pits, so you could walk up and ask questions and literally stand next to the cars.
I was standing next to a 70’s F1 car when they performed an engine test. I was wearing thick, professional earplugs and the biggest Peltors you’ve ever seen. When they fired that thing up, I lasted all of five seconds before I walked out. At that point, it was no longer sound but sheer pressure. You could feel it in your chest.
As for how the mechanics do it? Easy, they’re all deaf as a post. Even the best earpro can’t prevent that kind of hearing damage, especially if that’s your chosen career. If you’re worried about good earpro not being enough, best advice is to put distance between you and the object/career path involved.
When I was in the Army they put us in a room with a jet engine bolted to a concrete block, and the exhaust routed outside of the building. They fired that thing up and it was overwhelming. My hearing is fucked up today, and I sometimes wonder how much of the damage was due to that demonstration. Standing near a fucking Howitzer without ear plugs when it was fired off probably didn’t help much either.
At that point, it was no longer sound but sheer pressure. You could feel it in your chest.
I wonder if there would be a way to counter that though. Maybe some kind of sound-focused bomb suit developed for a single profession?
I imagine most situations are avoidable with modern technology allowing us to do things remotely but perhaps there was something used historically or as part of a “because I can” experiment.
Space-suits must operate this way, if inadvertently…
The number of decibels at the rocket-nozzles is waaay higher than what it would be “at the top of the candle”, but … there’s pretty-much nothing in Nature as loud as those things are, except meteorites, maybe some volcanoes, being inside of lightning, etc…
There was that Nathan For You episode where they locked that kid in a coffin and had an orgy outside to test the sound proofing. No real practical use but apparently it did a good job.
All jokes aside, I’m very interested to hear if something exists to that degree of practical hearing protection. Maybe a "suit"of sorts to cancel noise and dampen bone conduction or super active noise cancelling?
I did some research about this for myself, the best I could find is an advertised -45dB (Remote Audio HN-7506), which makes me very skeptical, I couldn’t find any third party measurements but multiple reviews I read mention that they have about the same isolation as Etymotic earphones.
Active noise canceling is good but only for lower frequencies, it does almost nothing to mid and high frequencies, which is not necessarily a bad thing since mid and higher frequencies are easier to attenuate passively.
The best noise canceling headphones have an average noise cancellation of -27dB (-20dB in the bass frequencies), but the best noise cancellation that I could find (other than the HN-7506 that I don’t really trust) is from Etymotic earphones, they are completely passive and have an average attenuation of -32dB with -21dB reduction in the bass frequencies which is really impressive, they work so well because they are inserted much deeper in the ear which can be a bit uncomfortable. I read a lot of experiences from musicians and apparently if you use foam tips instead of the stock ones you can get even better isolation and slightly better comfort.
Another option is custom molded IEMs or earplugs, I couldn’t find measurements for those but based on comments from people that have them they seem to have slightly less isolation that Etymotic earphones but they’re are obviously infinitely more comfortable since they’re custom molded to your ears (there are also soft wraps that increase isolation but I don’t know how effective they are).
So if you want the best noise cancellation I recommend the Etymotic ER4XR or the Etymotic ER2XR (afaik most Etymotic earphones have the same body (so same isolation), choose them based on the sound signature you prefer), if you want good balance between noise cancellation and comfort get custom molded earplugs or IEMs.
My sources:
Headphones with best ANC measurements, Etymotic measurements (click on Isolation on the sidebar)
Active noise canceling is good but only for lower frequencies,
Can you define lower here?
In my experience, they’re most effective for higher frequencies (voices and higher), as lower frequencies are hard to attentuate (why we can hear/feel subwoofers from cars a fair distance away).
For example, a couple pairs I have are ineffective against the bass from the gym idiots running the aerobics room (wtf does it have to be loud outside the room - those women must be getting hearing damage), but it’s great for all the people talking, and some of the tvs.
I don’t know the exact frequencies but it’s something I read and noticed myself, and wikipedia seems to agree.
Active noise cancelling is best suited for low frequencies. For higher frequencies, the spacing requirements for free space and zone of silence techniques become prohibitive.
(Don’t know what that means.)
Personally I used the Sony XM3 a lot, on planes etc. which have great ANC, and I also used the Moondrop Blessing 3 which are just normal IEMs with no ANC and I only notice a difference in the low frequencies, you can also see that in the rtings measurements (XM3, Blessing 3), isolation in mids and treble is about the same, they seem to consider anything under around 250Hz as bass.
Yea, that “low frequencies” is rather ambiguous.
I could see over-the-ear headphones being better at “lower” frequencies than in-ear, both from material absorption and speaker size. Every ANC pair I’ve had, of any style, was pretty good at nearly eliminating the higher frequency noise while flying (engines, airflow noise, etc), and almost eliminated voices.
I know nothing about this subject, but my instinct would tell me that anc would actually be protective. If you phase out sound, it seizes ceases to exist, right? That is the whole point of it?
Again, pure instincts, don’t know shit myself.
*ceases, FYI (not being snarky, maybe autoincorrect got you on voice to text)
Edit: also “seizes” used here was kinda funny
ANC isn’t protective in any way. If anything it’s probably just as damaging.
That’s just not true.
Your ear largely hears things through changes in air pressure. Projecting the same frequency and amplitude at the opposite phase prevents the change in air pressure in the first place. It’s literally cancelling the sound.
This is partially correct, partially wrong.
As many have commented, flipping a signal by 180° cancels it out. However, this is only true for static noise though. Transient noise cannot be canceled out completely, because you would need to see into the future to know which signals to play to cancel out the noise.
The ANC headphones I own mainly cancel noise through passive shielding of the ears. The “active” noise canceling feature is not contributing a lot.
The cone of silence obvi
