How loud do power tools have to be to hurt your hearing?

[Steve Blackdog]

Hi Folks,

I have just been looking at various shop machinery. I was dutifully reading the decibel levels without really understanding what they mean in real terms.

Whilst googling I stumbled across the American Tinnitus Association's website that is very helpful about what decibels really mean in practice. I know you can get this information elsewhere, but thought other people may find this as interesting as I did:

http://www.ata.org/for-patients/how-loud-too-loud

I have reproduced this, which I hope they won't mind:

"The loudness of sound is measured in decibels (dB). Most experts recommend that you use earplugs when exposed to 85 dB and above. But what does 85 dB mean? The following chart shows common sounds and their associated sound levels.

Ticking watch: 20 dB
Quiet whisper: 30 dB
Refrigerator hum: 40 dB
Rainfall: 50 dB
Sewing machine: 60 dB
Washing machine: 70 dB
Alarm clock (two feet away): 80 dB
Average traffic: 85 dB
MRI: 95 dB
Blow dryer, subway train: 100 dB
Power mower, chainsaw: 105 dB
Screaming child: 110 dB :roll:
Rock concert, thunderclap: 120 dB
Jackhammer, jet plane (100 feet away): 130 dB"


It links to this US govt site that has a rather dinky noise 'o'meter, which I liked:

http://www.cdc.gov/niosh/topics/noise/noisemeter.html

On with the ear defenders. Although, reading the list above, Motorhead and Status Quo probably have left my hearing irredeemably damaged :lol:

Cheers

Steve

 

[Cheshirechappie]

Pardon?

 

[TheTiddles]

That information is rather missleading I'm afraid, noise is relative to how near you are and more importantly, what weighting method is used, those are probably dB(A) @ 1.0m. You also get TTS (temporary threshold shifting) where the body adjusts its sensitivity according to the level of stimulus, examples of this are being a bit deaf after using machinery for an hour, night vision etc...

Anyway, cumulative exposure to above threshold levels is the root of hearing loss, so ear defenders are a good plan, nothing scientific there...

Aidan

 

[kostello]

i read once that a 25 year old carpenter has the hearing of the average 45year old..........................

anyway..............for the last 8or 9 years i've worn those in the ear plugs all day.................and they seem to work a treat

 

[MickCheese]

I have ridden motorcycles for 35years and have worn ear plugs for the last 12years without exception. I know that my hearing has been damaged over the years so wearing hearing protection now is my attempt at stopping it getting worse.

Mick

 

[t8hants]

When I was in the boat-yard in the 70's, we used to cold knock down alloy rivets, about 3,000 per boat as I remember. Sam and I were clocked at 134 db, the weekly 'safe' exsposure time for that was about 15secs, and despite having bought the first pair of ear muffs seen in the yard I now have a nice high pitched whistle in my left ear.

This ranges from so loud I am surprised the wife can't hear it, to as now barely noticable, but it is always there. Although twice last year it stopped, once for about 24 hours, man was that weird, I was almost glad when it came back - normal service had been resumed!

I have not heard of any problems associated with the long term use of ear defenders, so I should wear them if you are in any doubt, cause you don't want what I've got. (hammer)

Gareth

 

[ade1]

cannot stress enough the pros for using ear plugs and defenders, even for the quickest of jobs where it takes longer to put defenders on than it does to saw through a piece of wood! had tinnitus for about 2yr now, like gareth above its just in my left ear & can range from mildly annoying to wanting to bang my ear with a mallet to make it stop (haven't tried it yet though!). i think it started after we had some contractors in at work to use ice blasting machines on my print press to get rid of all the hard ink, was ok until they started using 2, we started complaing after a couple of days, even wearing ear protection, the safety guy came in and took some sound measurements & after that only 1 machine was allowed to be used at a time, although i couldn't say there was a defining moment where i realised there was something wrong with my hearing, just sort of started noticing it late at night mostly after telly off and dead quiet. not worth the risk, get those ear defenders on!

 

[Modernist]

All very true, although it is tempting not to bother when you are young. I am pretty deaf from shooting and machinery and Hendrix but it recently got worse after some site work in noise.

Perhaps I should relate my experience of and EMT specialist last week.

How old are you

60

You have obviously been exposed to some very severe noise

Yes

Nothing I can do for you, good morning.

WEAR YOUR EAR DEFENDERS WHILST YOU HAVE SOME EARS TO DEFEND

 

[Sawyer]

Two essential points here:
1. Ear defenders are cheap and very, very easy to use.
2. Hearing loss due to ambient noise is a gradual and insidious process. Once lost though, it's gone for ever.

I don't know about decibels, but for me, loud noise feels uncomfortable, and the moment I sense any discomfort, it's on with the ear defenders. That means most machining and nearly all power tools.

My original mentor, who had entered the industry in the 1930s would never wear them, even for thicknessing wide boards. "Noise, what noise?" He used to laugh. His opinion (which I always considered overly cynical), was that they were invented by the bosses to discourage workers from talking to one another!

I should add, that most of things I said to him needed to be repeated, whereas 30 years later, my own hearing is still pretty good.

 

[marcros]

these things are pretty good, which allow you to hear a conversation but protect you from the dangerous stuff

http://www.noisebreaker.com/

 

[TheTiddles]

If the noise is uncomfortable then it's already way over the safe level. Different frequencies are more damaging than others, most of what does the greatest damage isn't what you can hear, for instance the sound of gunfire that can be heard doesn't do as much damage as what you can't hear (the high pitch retort), I stay safe from this by avoiding people shooting at me.

Aidan

 

[woodbloke]

... I stay safe from this by avoiding people shooting at me.

Aidan

...difficult when we live in Salisbury and we can pick up the sounds of the artillery coming from Larkhill on the plain! I jest of course, but I can often hear this dull, muted booming noise coming from the North and I worked out the other day that it must be coming from Larkhill - Rob

 

[Eric The Viking]

Aidan is right: generally speaking it's impulse noise that's by far the most dangerous. That's sudden loud things, basically.

There was some chilling research done in Russia in the early 1980s. They found a village where pretty much the only employer was a drop forge. Adults, male and female either worked there or didn't, so there were easy comparisons to be made. It took about three months to cause a notch between 2kHz and 4kHz - just the part of the spectrum you need for speech sibilants and formants ("S," "T" and "P" sounds and other hard consonants). Shooting will do this, riveting, blacksmithing, pneumatic drills, and so on, in a very short time, and the damage is permanent. One of the biggest issues is that you can't feel the damage happening with this sort of noise. Drummers are a classic example of people deafening themselves without realising it.

Then there is broad-band noise exposure, such as jet noise at an airport. This also reduces the ear's sensitivity, but in a more broad way. Anything up to the threshold of pain (125dBa, generally speaking) will cause damage depending on exposure levels. It's been proven with reference to Berber tribesmen in the Sahara that this damage is cumulative too. The hearing of older tribesmen (70+) has been checked and found to compare with well with the hearing of younger people. It follows that deafness in old age is almost always caused by environmental noise exposure.

Some unexpected things can damage, such as SDS drills. One reason is that, like light, sound intensity follows an inverse square law, and such drills are inevitably used very close to the person's ears.

In nature, the only common really loud sounds are waterfalls and thunderstorms. Both are loudest at lower frequencies, and the ear copes well with them. It copes badly with high energy high frequency sounds, such as those from planers and circular saws. As a very small child, I remember running from the mill when the planers and big saws were working - it wasn't just frightening, it hurt. Small children are obviously pained by loud noise, but we learn to endure it (not necessarily planers!).

The other thing to watch out for is the personal stereo. Until the advent of digital recording techniques, it wasn't in practice possible to record and playback things like drum kits and gunshots in a way that made them dangerous. Analogue techniques 'soften' the transients (sharp leading edges) of the waveforms, taking much of the dangerous nature of them away. Now with digits (not you, Roy!), they can be reproduced in all their 'glory'. The trouble is that the sound sources are only millimetres away from the eardrum!

I've spoken to audiologists who think our present youngsters may become an entirely deaf generation in middle life, because of personal stereos. That's probably paranoia, but if you can hear them when you're sitting next to someone on the tube, or even the bus, that's definitely damaging the owner's hearing. Imagine how much mechanical energy is hitting the eardrum if you can clearly hear what's leaking out.

IPods, etc. are a concern for us, as the temptation is to use them inside ear defenders in the workshop. This is like being on the tube - the ambient noise means you wind up the personal stereo's volume even higher than normal (even though the ear defenders are helping it's not enough), and that causes damage. A way of getting round this, although it's not very convenient, is to use earplugs under conventional headphones. I do this on long haul flights, and it has the effect of enabling you to ignore the jet noise. I'd wear earplugs if I was commuting on the underground.

As has been discussed, if you're over 55 or so the damage has probably already been done. But if you're starting out in woodworking, get good ear protection and use it, if necessary ear plugs worn with ear defenders for the really noisy stuff.

As for 'noise cancelling' systems, for us they simply don't work safely. Don't even think they might.

I'm only banging on about this because I used to be an audio engineer and my hearing was my living. It's such a shame to talk to older colleagues now, who mixed a lot of rock and pop music in the 1980s, who now have serious hearing issues. What an unnecessary waste!

Hope that's helpful,

E.

 

[theartfulbodger]

Sobering post, Eric! I spent a dozen of my working years in a nightclub 4 or 5 (sometimes 6 :| ) nights a week.

Nowadays I use ear defenders :idea:

 

[MikeH]

Eric, What do you mean about noise cancelling systems not working safely?

I use NC headphones (ear buds) with my IPOD regularly when I travel from Devon to Reading on the choo choo, work great in my view, means I can listen to my music at a fairly low level and still get most of the train noise filtered out.

 

[Eric The Viking]

Train noise or aircraft cabin noise is one thing; woodworking machinery is probably 20dB (approx. 100x) louder, and at frequencies noise cancelling equipment cannot easily work at. Furthermore the technology becomes inconsistent with loud point sources in close proximity.

IMHO you can't beat simple attenuation. Noise cancelling's probably fine for travel (and it certainly works for military/comms applications), but for machinery exposure, it's not worth taking the risk. Your mileage, etc.

Cheers,

E.

 

[TheTiddles]

Noise cancellation works by creating the opposite waveform to the one you can hear. Fine for low level noise, apply that to a damaging level of sound and the system will create the opposite wave at the same volume to cancel it out, this would not be good for you! That's why they aren't used for loud noises, just annoying ones.

Aidan

 

[Jacob]

....
Anyway, cumulative exposure to above threshold levels is the root of hearing loss, so ear defenders are a good plan, nothing scientific there...

Aidan

Absolutely. Have had a hearing aid now for a year. The missing frequencies are typical of woodwork machinery apparently - higher frequency machines with brush motors being the worst.
You don't need to know anything abt decibel levels - if it's loud you need earmuffs.

 

[artfu1d0dger]

Ive worked in ship building for 25 years and make sure that members of my team use both ear plugs and ear defenders when working with or near loud machinery. we also supply anti vibration gloves to try and reduce the risk of white finger when using pneumatic tools.

Neil