[Elecraft] [K3] Hearing aids, meet K3

[Jim Brown]

On 8/6/2013 8:45 PM, Don Wilhelm wrote:
> I may b unique because my lower range hearing without the aids is 
> normal, so I have built-in low pass filters in my ears.

That's entirely normal, Don. In general, hearing loss starts at the high 
end and moves down.  Many folks with a lot of hearing loss still hear a 
lot of low end. The exception is when for one reason or another we are 
exposed to strong noise at a specific frequencies, or a specific range 
of frequencies, in which case we develop a notch in that range.

The problem is that speech intelligibility depends on sounds in the 
range of 500 Hz - 4 kHz, with the 2 kHz octave being most important, the 
1 kHz octave close behind.  That's why telephones and ham radio, with 
bandwidth limited to about 500 Hz to 3kHz,  work just fine. Energy above 
4 kHz helps, but energy below about 350 Hz makes no contribution, and 
often makes things worse.  The scientists at Bell Labs figured this 
stuff out early in the 20th century.

73, Jim K9YC