[RFI] Adding AFI to the List?

Roger (K8RI) k8ri at rogerhalstead.com
Mon Feb 2 15:02:39 EST 2009

kd4e wrote:
> I would like to humbly suggest that we add AFI to RFI, TVI, and EMI
> as a technological nuisance.
> At 1:30AM this morning AFI (audio frequency noise) emanated from
> the adjacent QTH loudly enough to wake me - screeching guitar and
> thumping drum sounds.
> We have previously discussed neutralizing the source of thumpa-thumpa
> amps in vehicles and muffler-challenged off-road vehicles using radar
> and microwave pulse-canons but have found them too power-hungry
> and too dangerous to humans and pets.
The technology for doing this is relatively simple for a small area as 
in a head set.  Aviation's been doing it for years and Bose sells ANR 
head sets for listening to the radio, but doing so for a large area and 
one with irregular shaped rooms is not.  Ever notice how you can walk 
around the house and hear a refrigerator in some places and not in 
others? Some of the modern, high efficiency ones can be quite loud. Even 
for a room size unit, phasing for different frequencies and locations is 
likely to be a problem, but it would take very little power compared to 
the source.

Fighting sound with sound although  very tempting and sometimes 
effective, usually has some bad side effects and may end up making the 
one suffering into the bad guy.

> We have also proposed detecting the audio waveform and generating
> opposite-cycle sound waves to cancel them -- but that received little
> response -- I am guessing it is too computer-intensive and would require
> too much power in an uncontrolled outside environment.  (Not sure if
> generated to mitigate only those sounds which penetrate the building
> that power-level or complexity would be as challenging but I lack the
> knowledge to build such a gadget and the funds to purchase them.)
Bose makes a nice headset...kinda pricey though.

73 and good luck,

Roger (K8RI)

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