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 | TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2002-03-18 36476
Just a note that might be of interest to some people.
I accidentally ran across a simple sound spectrum analyzer I used back in the sound buz days. I got curious about the sound curve for my Ford 1710. I had to remove some late March snow today so I analyzed my diesel noise. The results are below.
Ford 1710 Sound Level Curve (Not weighted) @ PTO RPM Unloaded
HZ DB
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31.5 92.5
63 95
125 97.5
250 95
500 92.5
1K 90
2K 90
4K 87.5
8K 85
16K 85
The sound was measured from the operator's seat outside, under a steel canopy and using the slow reading position on the analyzer. Slow readings can be interpreted as 'continuous levels.' Slow readings may miss some higher short-term sound levels.
The levels are generally around 90DB, which is high enough to cause hearing damage if exposed for prolonged periods. The curve is loaded at the low frequency end, which might be expected. However, I did expect to see one of the higher frequency bands peaked up due to diesel pinging. However, even without peaks at higher frequencies, there's still plenty of sound energy in the 2k - 4k range, which is range that is most damaging to hearing.
It's a little difficult to interpret DB figures. 70 DB is about the level of normal speech at say 3'. Sound levels decrease according to an inverse square law and loose 6 DB if the distance from a sound source is doubled. The tractor is about 20DB above speech levels but it also is much richer in high frequencies.
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 | DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada
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2002-03-18 36480
Wow Tom, cool numbers. Now you can help us nimnals. Do we need hearing protectors? Fifty some years on the planet, a couple hundred hours in little airplanes and hundreds more teaching police recruits to shoot has left me no hearing that I can spare. If you know, can you recommend a level of hearing protection? Foam plugs? Big mouse ears? ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-03-19 36489
Most of my hearing loss came from being a musician and live sound engineer. I had a set of linear 15DB custom mineral fiber plugs made to protect myself while engineering.
I wear the custom plugs when on the tractor. They are good for sound engineering because they don't colour what you hear too much. Foam, including 'clam shell' types, sop up higher frequencies and make everything sound muddy but they also provide around 30db of cut. Of course, the higher frequencies are what cause most hearing damage so maybe they should be sopped up except for sound engineering.
The question with foam plugs is whether an operator can hear everything they need to hear. Relief valves, set parking brakes and failing bearing all make high frequency sounds that might be missed. It's sort of a matter of personal preference. I use my 15DB plugs because I don't like muddy sound, but the 20DB version of these plugs may be preferable. Foam would provide better hearing protection. However, I do use the clam shells on my chain saw hat when chain sawing. I figure there's nothing much I want to hear then anyway.
There’s no good way to say how much damage a several hour exposure to 90DB of broad spectrum sound will cause for a particular individual. Hearing protection is a good idea for all equipment operators though--the damage sort of sneaks up on you. It is cumulative and irreversible over a lifetime, although I think recently developed surgical implants can make improvements. Incidentally, some outdoor stadiums impose max 90DB sound-level limits at the rear of audience areas. I’m not sure if the concern is with hearing damage or with noise complaints from near by residents.
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| MarkS
Join Date: Posts: 1 
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2002-03-19 36494
TomG, you bring up a good point with failing componets while wearing hearing protection. I Usually, and I must say usually, wear some form of hearing protection if I know I'm gonna be out mowing etc for the day. But, it is a little annoying to not be able to hear the tractor while you are working. I periodically remove the earplugs/headphones etc just so I can hear what is going on with the machine. It takes some getting use to using hearing protection and a little faith that your machine is in good working order and hopefully nothing is gonna fail. But all in all I'm sure your better off in the long run. ....
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| Clemson
Join Date: Jul 2003 Posts: 13 South Carolina
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2002-03-19 36504
I find the EAR foam plugs very comfortable to wear for extended periods. I, too, am a shooting instructor, so it is important to protect what I have left. I wear both plugs and earmuffs when I shoot handguns. The plugs alone are sufficient for my Massey Ferguson tractor. My machine, by the way, has the exhaust routed out low, below the transmission. Have any of you compared a low mounted exhaust to an identical tractor with a conventional stack going up in front of the operator? ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-03-20 36527
I story I may have spun here before is about middle-ear muscles. They are the fastest muscles in the body and act as compressors to protect against high sound levels. They also act whenever a person speaks. That's why babies and drill instructors don't go deaf. It's also why artillerymen say 'ahhhhh' before firing.
These muscles aren't completely quick and don't protect against high-energy transients of which there are plenty in shooting. Unlike artillerymen, riflemen can't say 'ahhhh' all the time, so shooter’s muffs are good.
After exposure to continuous high sound levels for awhile these muscles stop releasing. They are still providing protection, but that's the reason why everything seems so quite during breaks at loud concerts and the band can start up again and it doesn’t seem so loud. After longer exposure, these muscles just give up and stop providing much protection. That's when serious hearing damage starts. There can be injuries and overuse syndromes to these muscles just like any other muscle. People who mention having felt swollen and burning ears after concerts are reporting something like an athletic injury.
A conclusion is that's it's best to leave hearing protectors on when operating equipment or when sound engineering. However, the body's own protection usually is available if the protectors are removed for short periods. It is a little tough to keep protectors on if you think you're missing something. It's especially tough in sound engineering because you can end up with an audience that has a bad time. Plugs are almost impossible when playing live because the stage sound is loud but absolutely terrible in many places.
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