[Elecraft] OT: Hearing Aid Advice

[Jim Brown]

On 5/1/2012 8:44 AM, Fred Jensen wrote:
> Jim, K9YC, pointed out to me that I can get
> close to 30 dB of equalization from the RX equalizer simply by starting
> the lower freqs, which is where I hear, at -16 dB, and then setting the
> overall audio level to HI and running the AF gain higher.  This
> theoretically gives me 32 dB of differential equalization.  I've done
> it, it's nowhere near enough for me, but it sure does does help.

An additional clarification about why and how this works.  Hearing loss 
tends to vary with frequency from person to person, depending on their 
noise exposure and various physical conditions that can cause hearing 
loss. In general, hearing loss tends to be greatest at the higher 
frequencies. The best hearing aids use very sophisticated DSP to 
compensate for the frequency response of he loss, and use directional 
mics.  Etymotic Research is one of the major mfrs of the DSP and the 
mics, and their engineers are members of the Chicago section of the 
Audio Engineering Society.  I know some of them fairly well on a 
professional basis.

The frequencies that carry nearly all of the intelligibility of human 
speech are between 400 Hz and 5 kHz, and the range between about 700 Hz 
and 3 kHz is the most critical.  From an intelligibility point of view, 
everything below 400 Hz is noise.  Since hearing loss is greatest at 
higher audio frequencies, we can set the RXEQ in the K3 for maximum 
suppression of the four lowest bands and maximum boost of the three 
highest bands. This provides about 32dB of compensation for "typical" 
hearing loss. Fred has pretty severe hearing loss, so it's not enough 
for him, but as he notes, it helps.  For many it may be enough.  I have 
moderate hearing loss, and when my wife and I are listening to NPR or 
watching movies on Netflix, I turn up the highs and turn down the lows 
to improve or understanding of speech.

73, Jim K9YC