Hearing Protectors

[Newton Hunt]

Jim Bryant wrote:
". . A harmful noise level without use of a noise canceling device is
just as harmful with the use of one."

Jim, this is not true.

I have had a Noise Buster for several years, when they cost $175.00.
They are now 1/4 the size and cost about $75 at Brookstone.

The idea of active noise cancellation has been around since the
sixties.  A short science fiction story about noise absorbing/canceling
technology was a great boon to New Yorkers with traffic, air hammers,
subway and bus noises, etc., etc., until the cancellation container
became full and then exploded letting all that sound out at once.  BIG
NOISE.

This technology has been used for several years at grain elevators where
the exhaust of the grain sucker is extremely noisy, but with this
technology the noise is reduced immensely, to a tolerable level.

Saab is using it in their newest jet liners for passenger comfort.

Lotus used it in one of their cars and got sued because they used
patented technology.

Noise Buster company is working on one they call the muffler, the idea
is to place a microphone in the exhaust pipe of a car and speakers under
the car to cancel engine noise.  Maybe not a dumb idea, but I think I
would rather have the systems installed _inside_ the car to make the
passengers more comfortable.

Any noise that does not reach the ear is a non noise, period.  Active
sound cancellation technology has been around for some ten years and is
still an emerging technology.  I have had several conversations with the
technicians of the company making the Sound Buster and admire the work
they are doing, even though it is slow.  There are several models of
Sound Busters from the commercial one we speak of up to installation
inside noise proctors used by jet engine mechanics and airport workers,
some with built in radio communications.

It is true, if the noise is intense enough to be felt by the body, but
not the ears, then fatigue can be an issue.

If the sound level is only at that level that the sound buster can
handle the sounds entering the ear are zero, except generally above 3K
Hz, which are only attenuated slightly by covering the ear with the
phones.  If you consider the wave length of any tone above three
thousand Hz you will realize the physical limitations of a microphone,
the ear speaker and the ear channel present.  IF the sound is greater
than what the NB can handle you get distortion, leakage and cancellation
cancellation, or noise.

Safety has been a prime issue for the manufacturer and their literature
indicates buying the proper device based upon usage.

The microphones are located as close to the ear hole as possible.  The
sound is picked up before it enters the ear, processed and equalized to
compensate for the response of the microphone and the ear speaker then
the speaker produces a sound that is 180 degrees out of phase to the
sound entering the microphone.  The two sounds cancel each other out so
there is no SPL, sound pressure level, entering the ear.

The ear is protected from damage and from fatigue.  Mine is the first
consumer product on the market and is more cumbersome and more power
hungry than current products, but the are wonderful pieces of
engineering.

There is an input for a CD or tape player or for the output of the SAT
so one can hear the unison and tune them SOLID.  I also find the set up
useful for teaching tuner to hear the beats.

Now isn't that more about noise cancellation than you ever wanted to
know?

                        Newton