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AZSORT
11-14-2004, 08:59 PM
Does anybody have any experiance with the expensive type noice-canceling hearing protection? I've got to spend time in some noisy pecan processing plants and am willing to pay for some good hearing protection but I've read some studies that say they don't really do much.

Thanks
Greg C.

Dave Opincarne
11-14-2004, 09:21 PM
The one's I've seen don't seem to be true noise cancelation hearing protection. A close reading of the description seems to describe a microphone that cuts out above a certain noise level. YMMV
My hearing protection has a NR rating of 29dB http://www.leadersafety.com/show_prod.php?proID=129 This is as high as I can find in a head set and are well priced. This can be combined with in the ear type protection for extream situations. This is the method recomended in hearing conservation programs. The last time I had my hearing tested the Audiologist said he wished he had my hearing.

Dave

aboard_epsilon
11-14-2004, 09:59 PM
I remember a computer prog that was designed to do this .
it played back the exact opposite negative waveform in near real-time.
they have been experimenting with it on busses in europe to quiten engines .
for it to work properley i think you would have to have a microphone wired up to every machine in the shop and a speaker besides each of them.
because sound travels at 690 or so mph accordiong to height above see leval and air pressure...correct me if im wrong.
the headphone idea is to have a microphone and speakers near your head ..so not neading the above.
search google on the words anti-noise...you never know you may find a free prog to download.
all the best...mark

Evan
11-14-2004, 10:03 PM
Mark,

You have it right. They have even been experimenting with noise cancelling mufflers for heavy equipment that uses out of phase sound to cancel the noise from the engine. It's not a sly trick. If you can put out the exact same noise as the source but 180 degrees out of phase then the sound waves will cancel.

ibewgypsie
11-14-2004, 10:16 PM
We use ear plugs inside ear muffs for extreme conditions..

BOTh work together..

Last time I was exhausted from sound.. the hydro plant was spilling and the whole dam vibrating, I was working in the draft Tunnel about 100 feet down, below actual water level.. I was physically and mentally exhausted from the shaking and buffeting of the noise.. Every muscle was quivering when I left that day..



------------------
David Cofer, Of:
Tunnel Hill, North Georgia

Dave Opincarne
11-14-2004, 10:38 PM
One curious effect of using the muffs and plugs in combination is sound appear to be comming from the opposite direction. I'll think someone is speaking behind me to my left when they're standing to my right. I wonder if this could have something to do with the attenuation of my muffs to the range of human speach. Any ideas?

Dave

WJHartson
11-14-2004, 11:10 PM
I bought a set of the noise cancelation type head set in about 1997 from Noise Cancelation. Think they have been bought out by someone like Walker muffler. Know they were trying to develop a way to reduce the exhaust noise on large busses and trucks. I tested them in two high noises areas, turbine floor in a powerhouse and in a blower room. They worked better than anything else that I had tried. You could carry on a conversation in both areas with a person with the same equipment. Could not do this with normal hearing protection. THe units canceled frequencies in some of the ranges. If I remember correctly I paid about $300 a piece for the headsets.

Joe

Jerald Ware
11-14-2004, 11:23 PM
Some of the guys I shoot trap with have those muffs and swear by them for shooting. They say they can hear normal conversation and when someone shoots, the blast is blocked.

I received an email sales notice from HF and they had a pair there for only $19. Worth trusting your hearing to? I don't know-Jerald

Involute
11-15-2004, 08:38 AM
I use noise cancelling headsets in my plane. They work good for actively cancelling low frequency noise. Higher freqencies are reduced passively (like muffs).

As mentioned by others, there are also the microphone style that are standard muffs that play sound through the ear cup up to a certain dB level, then cut out.

One other thing... I've talked to some people that can't stand to where ANC headsets. Although there is a reduced noise level, the cancellation generates some "pressure" in the ear cup. It's a strange feeling, kind of a very loud quietness, if that makes any sense, something that you might want to try out before buying. I like 'em, though.

Evan
11-15-2004, 12:01 PM
Jerald,

Those type of hearing protectors work as a sort of pressure activated sound valve. The active electronic noise cancellation gear doesn't have a fast enough response time to protect against "impact" noise like a gun shot.

lunkenheimer
11-15-2004, 12:57 PM
Evan has a good point. There are two different types of active headsets-one is a noise limiter type which is like a regular earmuff except with a microphone on the outside and a speaker on the inside. These will limit the volume of the sound they transmit, but can't actually reduce noise. They do let you have a conversation without removing them.

The other type is 'active noise cancellation' which creates an opposite phase sound inside the earmuff to cancel the sound coming from outside. These can reduce noise better than passive muffs. They work better on medium and high frequency noises(they wouldn't help so much with shooting, for example) Bose makes some really nice ones but they cost about $1000.00 (not a typo)

Ian B
11-16-2004, 05:10 AM
Greg,

I've owned & used a set of Bose Quiet Comfort noise cancelling headphones for a couple of years - they work extremely well to cancel out constant, unvarying noise. I use them to eliminate background turbine noise, and they cancel the noise completely.

If someone speaks, you can still hear them, but muffled. I don't think they'd work against a sudden noise (a shot, etc), but they're full muffle types, and this by itself would attenuate a lot of the noise.

The headphones come with a small box containing a battery and the electronics, and I paid $300 at the time. Check www.bose.com. (http://www.bose.com.) For me, money very well spent.

hth,

Ian

Ian B
11-16-2004, 05:10 AM
Greg,

I've owned & used a set of Bose Quiet Comfort noise cancelling headphones for a couple of years - they work extremely well to cancel out constant, unvarying noise. I use them to eliminate background turbine noise, and they cancel the noise completely.

If someone speaks, you can still hear them, but muffled. I don't think they'd work against a sudden noise (a shot, etc), but they're full muffle types, and this by itself would attenuate a lot of the noise.

The headphones come with a small box containing a battery and the electronics, and I paid $300 at the time. Check www.bose.com. (http://www.bose.com.) For me, money very well spent.

hth,

Ian

Jerald Ware
11-16-2004, 08:37 AM
Does anyone have any knowledge of the ESP brand out of Colorado? (www.espamerica.com, I think)
Their best digital is a bit pricey, $2K.

I have read the custom molded plugs shrink and if you gain/loose weight, they may not fit. I have a set of those I can't wear.

I have trouble hearing the dog beeper collars in the wind and sometimes I can hear them but can't figure out where the beeps are coming from when the dogs are on point.-Jerald

meho
11-16-2004, 10:00 AM
Hi Jerald,

You might find this type of electronic muffs to your liking: http://www.gamaliel.com/cart/customer/product.php?productid=5784&cat=224&page=1

They are stereo and that will allow you to pick up on the direction that the beeper is coming from. Shooters have worn this type of protection for years on the range with great satisfaction.

Muff style protectors are better than any plug type protection. I like my electronic muffs so well I gave my dad a set.

James

[This message has been edited by meho (edited 11-16-2004).]