Re: Directional Mic - using only aural tubes

> What you're looking for is some kind of design for acoustical cavity
> filters.  The phone company has always done pretty well transmitting
> 300 Hz to 3000 Hz for speech, so you need a low pass filter with
> cutoff above 3k.  

Cheers Tim.  I thinks you may have cracked it !  I'll look into it right away.