How Much Sound Can Enter via Bone Conduction?

[Benjaminbb]

Hey all,

I have mild tinnitus. I'm often around noise, so I protect my hearing.

I have tried to protect my hearing for most of my adult life. Age 20 onwards. I'm always using earplugs and always correctly. I use lower dB rating earplugs in bars and restaurants, and 20-30 dB rating earplugs at concerts.

Meaning I'm frequently reducing loud sounds to 70-90 dB at worst. I've just always disliked loud sounds.

Someone mentioned that, despite using earplugs, we can be exposed to loud sounds via bone conduction. But surely not enough to reach 90-100 dB and damage hearing?

Is it still safe for me to continue protecting my hearing like I've done thus far?

 

[linearb]

Hearing protection: surpassing the limits to attenuation imposed by the bone-conduction pathways

Previous studies will be reviewed that provide indications of the bone-conduction (BC) limits to attenuation that, in terms of mean values, range from 40 to 60 dB across the frequencies from 125 Hz to 8 kHz.

This implies that bone conduction muffles more than your earplugs can, meaning that you're not going to hit ranges which are unsafe due to bone conduction, until you've already exceeded the protection your earplugs were giving you.

However, I do note that this study only goes up to 8 kHz, and of course concerts are a sonic bath all the way up to 20 kHz. Generally, higher frequencies are easier to block, and this is certainly true of foam earplugs, but I don't know if the same is true of bone without more digging. The fulltext here would probably tell you, just look at the data sets and see if the "60 dB" protection was at the low end (125 Hz) or the high end (8 kHz) of what they tested. I would assume it is the latter which would mean that higher frequencies are blocked even more substantially.

tl;dr bone conduction appears to be more protective than headphones. No one can tell you what's "safe" because we're all different; also, "32 dB" rated earplugs do not reduce the sound to your ear by 32 dB across the board. The math here gets pretty complex, this may help:

Hearing Protection Calculator

If we use 120 dB as the bar for a "very loud rock concert", then we get this:

In the worst case scenario, a normal person using properly inserted 32 dB foam earplugs would only reduce the actual decibel at their ear by 13 dB, and would suffer hearing damage after a half hour or so.

I, personally, do still go to occasional concerts (or did, until COVID-19), but I find a spot where the ambient volume is high 80s to mid 90s with spikes not higher than the mid 90s to very low 100s, and hang out there, with hearing protection. If a show is louder than that, I just leave, and I don't tend to buy tickets for shows I expect to be loud. One of the last acts I've seem was Kurt Vile, an artist who has tinnitus badly enough himself to have mentioned it in at least one song.

My wife saw Aphex Twin a couple years ago; this is an artist we both love, but I decided to skip it because they are notorious for doing huge warehouse shows and basically trying to create an insane "wall" of sonic energy. She said that at one point the bass was strong enough that it literally knocked one of her earplugs out. Yeeesh, not for me!

 

[Benjaminbb]

@linearb,

Hey dude, thanks so much for your comprehensive reply.

Sounds like we have similar lifestyles. I definitely don't want to become anxious and just stop going out/doing my job.
I would love to go over this a little more if you know more details or if I'm missing something.

Re: bone conduction. Good to know.
I do think that the higher frequencies (8+ kHz) also don't conduct well through bone, that's pretty clear with any sort of bone conduction headphones or when blocking ears. It would be fairly similar to 8 kHz I'd imagine.

Re: the hearing protection calculator, interesting to see this NRR calculation as this is what I've been wondering/hearing. However, I took a a look at the earplugs I use and they are rated at 36 dB SNR, if you do the SNR formula on that page you'll see it actually does give the full range unlike NRR. Which would then be about 32+ dB reduction.

I had also read somewhere that these days those NRR or SNR ratings take into consideration how well a normal person inserts the earplugs. So that should already be factored in.

Do you have musician's earplugs?
I just got my musician's earplugs (with filters) rated at 17 dB SNR and they told me they're definitely a full SNR 17 dB reduction which, when I tested, sounded to me like about half the protection of the 36 dB foam earplugs I had been using. I'm used to far more reduction than this.

I'm going to get a higher rating earplugs too but they said these ones are the recommended reduction for "musicans and concert goers" The higher 26 dB & 31 dB ratings are for industrial noise for 8+ hours a day and car racing.

That would indicate to me that these are somewhat safe and high rated 36 dB foam earplugs would be very safe?

After seeing this I had also mentioned this NRR formula and low reduction above to my audiologist and they seemed pretty confused and said that the foam earplugs definitely do give you a huge reduction as advertised, at least as SNR in Australia.

My worry had been that it wasn't enough and that continuing to do music activities could be detrimental. Although I too would avoid 120 dB like you where possible.

What do you think of the above? Does this make sense or am I still missing something?

 

[Juan]

Kurt Vile, an artist who has tinnitus badly enough himself to have mentioned it in at least one song.

I like his music. I did not know he had tinnitus.

My wife saw Aphex Twin a couple years ago; this is an artist we both love

That one is interesting too. I have a CD, but honestly it gave me headaches, even at low volume. I have never seen Kurt Vile or Aphex Twin at a concert...

 

[Juan]

I'm going to get a higher rating earplugs too but they said these ones are the recommended reduction for "musicans and concert goers" The higher 26 dB & 31 dB ratings are for industrial noise for 8+ hours a day and car racing.

If you have tinnitus, hyperacusis or hearing loss, the only safe path is not going to these events, to loud concert, car races etc... there is nothing that can protect you from damage, not even double protection (earplugs and earmuffs combined).

The only protection stems from being far away from the noise source, meaning the sound reaches your ears at much lower decibel levels.

 

[linearb]

I like his music. I did not know he had tinnitus.

<Kurt>
When I was young, I liked to hear music blarin' and I wasn't carin'
To cover my jams with earplus
But these days I inhabitate a high-pitched ring
Over things
So these days, I plug 'em up

<Courtney>
When I'm struggling with my songs I do the same thing too
And I crunch 'em up in headphones, why wouldn't you
You could say I hear you on several levels
At high decibels
Over things

The fact that this is a an album by a "Kurt and Courtney" was lost on me until just now.

 

[Benjaminbb]

If you have tinnitus, hyperacusis or hearing loss, the only safe path is not going to these events, to loud concert, car races etc... there is nothing that can protect you from damage, not even double protection (earplugs and earmuffs combined).

The only protection stems from being far away from the noise source, meaning the sound reaches your ears at much lower decibel levels.

I agree it's good to play it safe, but where are you getting the info that even double protection isn't enough? I assume you're saying that there's enough risk for damage through bone conduction?

@linearb, did you see my reply above?

 

[Juan]

I agree it's good to play it safe, but where are you getting the info that even double protection isn't enough? I assume you're saying that there's enough risk for damage through bone conduction?

Personal experience. Yes, there is enough risk for damage even with double protection.

 

[Kriszti]

where are you getting the info that even double protection isn't enough? I assume you're saying that there's enough risk for damage through bone conduction?

https://www.osha.gov/dts/osta/otm/new_noise/#appendixe

Here you can see that double protection only provides 5dB reduction to the already adjusted, higher NRR rating of the two personal protective gears. If you go to a rock concert, that may not be enough, but of course, that's also individual, you seem to be doing good with your current protection method.