[RFI] Actually an AFI Question ...

[Jim Brown]

On 2/3/2011 1:47 PM, doc at kd4e.com wrote:
> Can low-frequency audio be canceled using sound?

At a single point, like in noise cancelling headphones. Sennheiser and 
Bose both make some that I would expect to work well.

> I seem to recall someone using sound to cancel echos
> in a hall to improve the acoustic qualities.

That is pure BS.  Sound and acoustics in public spaces is my field, and 
I can tell you with authority that it is NOT possible.
> Would it be possible to detect thumpa-thumpa loud car
> audio and transmit sound that would cancel that sound?

No.  You could reduce the level substantially in your ears with very 
good noise cancelling headphones, but most headphones can't produce 
enough level at very low frequencies to make much of a dent.

73, Jim K9YC