Electronic earmuffs fit

[Alantoo]

Comprehensive reply Alan ...I’ll read it more thoroughly later.

There must be some sound transmission through tissue, bone and the eustachian tubes as evidenced by the number of earpiece microphone devices that pick up clear speech that can’t come directly from the mouth....perhaps they do, phones are pretty good at that?

I’m thinking here of the Jawbone bluetooth phone earpieces......and years ago when doing firework displays, we had 2 way radios where the microphone was within the in-ear earpiece speaker and no bigger than a normal in-ear speaker ....so just the thin cable to go in under the chainsaw helmet muffs. (Think they’re still in the loft somewhere).

Perhaps we should remember to keep our mouths firmly shut when shooting ...never a bad thing!

cheers

fizz

Probably more effective to keep our mouths shut the rest of the time so we don't irritate or bore anybody when ambient is quiet enough for them be able to actually hear us!

Funnily enough my father always reckoned he was told in the army that to protect your ear drums you should keep your mouth open when you were standing beside a cannon, so that the air pressure was balanced either side of the ear drum...from ear canal and eustachian tube. I seem to remember he said it was fingers in the ears and mouth open. The attenuation by the fingers presumably matching the pressure transfer along the smaller eustachian tube.

Alan

 

[caorach]

Furthermore, calculation of the acoustic impedance mismatch between air and bone predicted at least 60 dB attenuation of BC.

This is the key point here and explains the problem fizz mentions.

Basically, if you consider water as a good starting point, if you shout at water almost all of the "sound" gets reflected back and this is because of the huge difference in the impedance between air and water - fish can't hear you talking.

You will see people claiming that ear muffs are better than in ear protection and, mostly, I suspect this comes from someone who had something to sell but it may also come from something Alan alluded to which is that in very, very high pressure sound fields then you can transmit some sound from air to your head and this can become a problem. My understanding, and there isn't a lot of info on this as it is such a rare and specialized field, is that this only applies under the most extreme circumstances in close proximity to very big guns indeed, Alan mentioned the interior of a tank where you are in an enclosed space with your head a few inches from a very large gun. Anything that I've ever read on the subject indicates that for small arms, and indeed any conditions encountered by almost everyone on earth, this is not a significant problem.

Bone, and flesh, conduct sound well, better than air, and so it is possible to build a transducer that if pressed against the flesh will pick up speech and convert it to an electrical signal. However, your head isn't good at "radiating" sound because of the impedance matching problem - it isn't matched to the air - but your mouth, vocal cords and so on are designed for this job

Generally speaking the biggest single difference in effectiveness between different hearing protection devices is correct fitment - if you don't put it on right, or if it doesn't fit correctly, or if your glasses interfere with it, or you aren't wearing it because it's uncomfortable etc. then you've got a much bigger hit to effectiveness than the differences between individual devices.