[Elecraft] W2IHY 8 band equalizer and EQ Plus

[Joe Subich, W4TV]

 > It is VERY well known that the most important octave bands for
 > speech intelligibilty are the octave bands centered on 1,000 Hz
 > and 2,000 Hz. Those bands range means from about 720 Hz to about
 > 2.8 kHz. The 500 Hz is next most important (extending down to
 > about 350 Hz), followed by the 4000 Hz octave band.

And in the 1000 Hz band, the important part is almost entirely
the upper third.  Human voice has almost no energy and nothing
that contributes to intelligibility between approximately 700
and 1100 Hz (with some variation in the beginning/end of that
dead band).  One can do extremely effective communications audio
with 300 - 600 Hz and 1200 Hz to 2400 Hz only.  Extend that just
slightly (200 - 600 Hz and 1200 Hz - 2800 Hz) and one gets audio
with very good "presence" (the low format) and excellent
articulation (the high format).

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.

73,

    ... Joe, W4TV

On 4/28/2010 12:29 AM, Jim Brown wrote:
> On Tue, 27 Apr 2010 22:49:14 -0400, Lu Romero wrote:
>
>> While I agree in principle, in practice, there are some high
>> frequency sibilance "formants" that need bandwidth up to and
>> including 2.8kHz to almost 3kHz to be well understood.
>> There are also some harmonics, especially in male voices,
>> that go down below 300-400 Hz.
>
> YES. Because I've made my living designing sound systems for
> highly reverberant churches, this is something that I've had to
> carefully study. It is VERY well known that the most important
> octave bands for speech intelligibilty are the octave bands
> centered on 1,000 Hz and 2,000 Hz. Those bands range means from
> about 720 Hz to about 2.8 kHz. The 500 Hz is next most important
> (extending down to about 350 Hz), followed by the 4000 Hz octave
> band. Human knowledge about this is VERY well established, and
> dates back to the earliest days of telephony. That's why it's so
> important to boost the mic response to compensate for the rolloff
> by crystal filters between 2 and 3kHz!
>
> 73,
>
> Jim Brown K9YC
>