[CQ-Contest] Filter???????

[k3bu at optonline.net]

Higher frequencies, high tones propagate more in line and attenuate faster.
Low frequencies, bass, tend go "flow" around the corners and attenuate slower.
Looks like your situation is creating filtering effect, attenuating higher pitched tones (noise) from the lower pitched tone of CW. The lower pitch, the better separation.
 
Some of the old design headphones managed to create mechanical resonance at particular frequency, cavity like effect and accentuate the particular pitch. To some extent this effect can be created by forming little "parabola" with your palm and positioning it to focus the sound on your ear and you can "amplify" sound or particular range of frequencies. Try that on the front of your speaker and you can also create some filtering and discrimination against the surrounding sounds.
 
73  Yuri, K3BU

> I've noticed something for years and just wonder if anyone else 
> has the same experience? This morning I was copying
> OH6AH on 40M LP but he was pretty weak and the background noise 
> made it a little difficult. The speaker was on and
> I needed to go downstairs to get something - as I descended the 
> stairs it seemed like a filter was switched in by my
> brain and all the background noise went away leaving only the 
> signal. Just like a nifty audio filter. In years gone by
> I have noticed this many times but never asked anyone about the 
> phenomenon. In Arizona I would be working in the
> yard maybe 100' away from the shack, the window would be open 
> and radio on and I could copy weak signals without
> any problem.
> 
> Comments?????
> 
> Tony W4OI/HK1AR
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