Hearing Protectors

[Ron Nossaman]

> And if the tree falling was not "perceived" as making  noise does that  make
>the tree any less fallen?

* Of course it fell, grasshopper, it just didn't affect anyone with the
resulting sound.




><<"  Noise cancellation headphones do not change your perception of reality.
>Jory">>
>
> Jory that is exactly what these dillys do.

* Disagree, the reality is modified on the output side. Perception remains
accurate.



><<"Please explain "if the level is high enough to damage hearing without use
>of this device it will still damage it even though the device is used" it does
>not make sense based on my knowledge of how the headphones work and my
>personal experience.
>Jory">>
>
>If the frequency deemed as being desirable of cancellation is such that after
>exposure there is some hearing degradation, for whatever length of time and at
>whatever level, the same degradation of hearing will exist after the use of
>any "cancellation" device.  What will not be present is the "fatique factor"
>associated with this noise as it concerns the decoding of this frequency, the
>"fatique factor" on the ear is still there though.

* This isn't an explanation, it's an opinion. What's the reasoning here?



> An example of this is infared light. True infared light cannot be perceived
>by normal visual acuity but visual acuity is effected by it nonetheless. If
>you point a remote control at your eye and key the control you will not be
>able to see the light as it strikes your retina but after you shut off the
>remote and close your eye you can "see" the 'burn' left by the light on your
>retina.  The same is true of these noise "cancellation" devices and ears.

* Infrared light is above the frequency range of visible light. Doesn't
compute as an example. If you are arguing that noise cancellation devices
won't do anything in frequency ranges beyond those for which they were
designed, that's correct, as well as being obvious, but that isn't what you
said. If whatever is 'left over', by being outside the range of
effectiveness of the device, is harmful, hearing is still at risk, but that
isn't what you said either. You say (correct me if I'm wrong in content, not
semantic details) that the damaging part of the noise gets through to your
ear in spite of the fact that it isn't measurable at damaging levels within
the frequency design parameters of the device. If you are correct, it means
that the engineers who design the devices, and the fundamental physics of
the acoustics involved are wrong. If that's the case, you missed your calling. 



>  Another example of this to be found, in tuning this time, is a three string
>unison where one string is tuned to pitch, the next string set at just
>slightly sharp and the last string set at slightly flat.  This note when,
>flatness/sharpness is equal, will be perceived as if it were in unison.....but
>is it?

* There is a whole lot of mechanical coupling and damping going on in this
instance that pull the pitches of the three strings closer together. This
isn't just perception, it's a real and actual modification of pitches
produced. The ear is hearing what the unison is producing. 




>While perception is your reality, perception doesn't change reality. (Faintly
>Dull)

* Neither does assumption. So your contention is based on your perception of
the realities of dynamic noise suppression, right?  



>  So for those who would like to depend on "cancellation" devices for
>protection, bless you go forth and prosper, but for the forseeable future I
>will continue to seek 'protection' when needed and 'cancellation' when called
>for realizing that they are not the same.
>Jim Bryant (FL)
>ps, If I am wrong about this, if won't be the first time that I have been
>wrong and probably won't be the last time either :-)

* Being wrong is easy, I've done it thousands of times. It always
(continually) happens to me when I don't have enough facts, and often enough
when I misinterpret the facts I think I do have. Happens every day. I guess
we're all still asking Dad why the sky is blue, where wind goes, and whether
fish sleep. (because, down wind, only when their eyes are closed)

 Ron