Re: Can inverse gravity waves cancel out Earth's gravity in selected areas?

On Thu, 26 Oct 2006 17:54:32 +0000, Tom Roberts wrote:

sal wrote:
Sound canceling headphones, like the ones available from Bose and Sony,
use this principle to make a "dead spot" at your eardrum.

And anyone who has ever used them knows how poorly they actually cancel
sounds. While they are an improvement over just headphones alone (e.g. on
an airplane), calling it a "dead spot" is a gross overstatement.

After shelling out <too much> for a set of Bose magic headphones I found
that they seemed to make the effect of computer noise in my home office
_worse_. It took me quite a while to figure out why: The electronics and
speaker elements are not fast and precise enough to cancel anything except
_low_ _frequency_ noise. (You need to dig around a bit to discover this
-- the manufacturers of these gadgets don't exactly shout this limitation
from the housetops.) In consequence, the stuff that typically wrecks
your ears -- the high frequency sound -- comes through unattenuated while
everything else gets quieter. (In fact it's even conceivable that the
headset produces some HF hash on its own due to mis-tracking of sounds at
the edge of the range it can cancel effectively, though I can't prove
that.) So, it _sounds_ like they're really quieting things down, but
somehow, at the end of the day, it didn't help all that much. In contrast,
conventional earplugs or a hearing protector headset seem to work better
on HF sounds than LF sounds.

When all the machines are powered on and the noise is really getting to me
I find that earplugs _plus_ the headset is a combination that works pretty
well.




Tom Roberts

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