Submitted 5 months ago by CorrodedCranium@leminal.space to [deleted]
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?
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. 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…
I visited a top fuel dragster event once. It was insane to feel th e pressure in my chest despite being a good 50-100m away from the cars.
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?
...they locked that kid in a coffin and had an orgy outside....
You just named a practical use.
All jokes aside, I’m very interested to hear
I see you…
You’d need the suit to allow you to “float” inside or it. Air gapped, and rubber suspension? Maybe some kind of a liquid, but it would probably just allow for more transference?
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:
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.
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 to exist, right? That is the whole point of it?
Again, pure instincts, don’t know shit myself.
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.
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.
I think we need to define “hearing protection”, and how far your willing to go
For example this is probably less than practical.
It should be noted that active noise canceling doesn’t actually protect your ears. It’s just pinpoint more noise into them (noise that happened to be exactly opposite in phase, but the pressure is still there.)
Wouldn't out of phase noise also cancel the pressure? The amplitudes combine to zero.
Yes.
Nope.
So what you hear as frequency is the variation of pressure- hi-low-hi-low-hi-low, right?
We tend to visualize it as a line going up and down, etc, but that’s just a conceptual aid.
To “cancel” noise, it plays a tone whose high and low pressure is out of phase but otherwise identical. So instead of hi-low-hi-low, it plays low-hi-low-hi noise, and you don’t “hear” it.
Great for tuning out the noise of a jet engine, and the loser who keeps trying to talk to you while you’re stuck in a tin can with a bunch of other sardines for 10+hours.
But that pressure is still there pushing against your eardrum, and no matter how good the pick up and driver is for the ANC, it’s never going to perfectly match noise anyhow.
There’s a reason most ANC ear cans are closed back- the passive noise isolation reduces the amount of work they have to do.
Active noise cancelling does reduce the actual sound pressure (that’s the only way volume can be reduced). See for example: en.wikipedia.org/wiki/Hearing_protection_device#E….
You understand that all of those devices have passive noise isolation, right?
What the electronics are doing is actually playing back noises that don’t cross certain thresholds. (Like people talking.) so you can “hear” them, but really it’s the speaker drivers you hear. The best will also filter out background noise, but the protection comes from the passive protection.
(Which is again different from acoustic filters, which basically create a chamber that alters the noise wave forms to passively attenuate things that are too loud.)
Hmm, I was under the understanding that it actually cancels out the pressure by creating a wave exactly 90 degrees off from the initial wave, creating reverse pressure and canceling the sound….
Not sure?
It pumps noise at other noise. All that noise literally cancels out. There’s literally no sound.
active noise canceling doesn’t actually protect your ears
I doubt that, mate.
The thing is that it needs to be literally perfect polarization flipping to protect you. ANC as we know isn’t perfect; it doesn’t perfectly cancel sound and create absolute silence. You’re still potentially vulnerable to high SPL
Show me electronic ear pro that doesn’t have passive noise reduction.
I’ll wait.
The vast majority are adding ambient low-level noise back in rather than removing loud noises with active noise cancellation.
The electronics are similar if not identical, mind, but there’s a reason active noise cancellation in things like the Bose headphones don’t get an NRR or SNR test done. Because they’re not ear pro
Your example made me wonder how effect coating yourself in sound padding tiles to the point you resemble a lychee fruit would be.
The cone of silence obvi
Offline open source AI pointed me to this article on Wikipedia:
Some HPDs reduce the sound reaching the eardrum through a combination of electronic and structural components. Electronic HPDs are available in both earmuff and custom earplug styles. Electronic microphones, circuitry, and receivers perform active noise reduction, also known as noise-cancelling, in which a signal that is 180-degrees out-of-phase of the noise is presented, which in theory cancels the noise.[1]
Do you know what the rated NRR is?
It points you in a new direction of research and information like any others here. Sorry I cared to ask and respond I certainly won’t next time.
I don’t exactly know whether this strat is redundant or not but I wear noise cancelling earbuds with full earmuffs overtop and it seems to do a good job. Plus i get the added benefit of being able to listen to music and hear phonecalls while on a machine.
Deafness.
explore_broaden@midwest.social 5 months ago
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: 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.