[Elecraft] W2IHY 8 band equalizer and EQ Plus

[Paul Christensen]

> It is also interesting that human hearing is most sensitive in
> the very area that the human voice has no energy.  Some have
> speculated that to be an evolutionary "defense" which allowed
> early man to hear danger in the middle of a crowd of voices.

There's actually quite a bit of short duration energy of the human voice at 
or near 3 kHz.  Interestingly, the classic Fletcher-Munson (FM) family of 
curves shows peak sensitivity to sound pressure level also at or near 3 kHz. 
The speculation by many speech pathologists, audiologists and researchers is 
that the presence band near 3 kHz evolved over time, matching an important 
part of human speech for maximum intelligibility near the 3 kHz octave-band 
region.

The 3 kHz peak is a function of the ear canal length.  As I recall from my 
psychacoustics studies at NIU, the ear canal length does not change 
significantly from the time birth to adulthood.  The resonance point on the 
FM curves is calculated as anyone would calculate the resonance point of a 
closed pipe.   The tympanic membrane forms the closure on one end of the 
pipe.

I would say that maximum articulation occurs at an upper audio cut-off near 
3 kHz, with diminishing returns above that point.

On the low end, it's easy to plot the lowest frequency generated by any 
voice.  Using FFT software and a sound card, I've measured the fundamental 
point of most male voices between 80-95 Hz.  That 15 Hz of difference may 
not seem like much, but the difference is significant.  I've measured only a 
few voices on the air that reach slightly below 80 Hz and when they do, 
they're the ones that could do well with commercial voice-over work.

Certainly any attempt to achieve a response in low-end audio below about 90 
Hz is a wasted effort.  Folks who adjust their low-end EQ to compensate for 
a lack of deep bass in their voices can do nothing to sound the way they 
really want to.  Either we were born with the gift or we weren't and no 
amount of EQ will change that -- excessive boost just makes it sound like 
we're trying to compensate for something we don't have and can easily create 
a phantom carrier when speaking in ESSB mode.

Paul, W9AC