First off, some weasel words: Do not construe what is said below as medical advice. Consult professional advice for YOUR own situation BEFORE taking any action! Do YOUR OWN research! Anything that is said, if you follow or use, you do so at your own risk, no warranty expressed or implied!
Do not taunt Happy Fun Ball!
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Having impaired hearing myself
(significant conduction deafness since I was very young - but the nerves are still in excellent shape even though I'm well into middle age) I would urge you to get your hearing tested - mostly so that you know what sort of condition it is for which you are trying to correct - and make certain that it isn't something trivial and easily fixed. The obvious one - earwax - should not be overlooked as my mother
(who is a retired nurse) can attest as that accounts for many cases of "deafness", often by those who absolutely insist this to NOT be the case until they are proven wrong!
Now, I'm not a spokesman for any hearing aid company
(I should technically be wearing at least one of them, but I do not as I have adapted to fill in gaps by lip-reading in the presence of other people as well as interpolate/extrapolate with very good accuracy the missing words/vowels/consonants in context - a skill that is NOT easily acquired and has taken decades to do so!) but it would be a real shame to throw amplification onto an ear in which there was already nerve damage - and then cause
additional damage with excess sound pressure level, wiping out/damaging what was left!
If one has conduction deafness, this is
(probably) less likely to happen as you are
(more or less) overcoming attenuation, but if it is actual nerve damage, one must be *really* careful to avoid blasting any sound pressure at a level that will cause physical damage - and without calibrated instrumentation and knowing what, exactly, the "inner ear attenuation" already is, you are essentially blind.
If/when you have ruled out that it is something that is trivial or something more serious that could actually be "fixed"
(e.g. wax, fluid buildup, cholesteatoma, etc.) walking away with your own, private "frequency response" chart for each ear would be invaluable in applying a "correction factor." At this point, you would presumably know what sort of hearing impairment you have
(e.g. conduction, nerve, combination, etc.) and know the risks that one might take when applying unknown (!) amounts of sound pressure to the ear.
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The world is rather lousy with graphic equalizer-type schematics and for starters, a simple bass/midrange/treble diagram would be appropriate: If you are typical of most, your most problematic hearing loss likely occurs in the 500-2500 Hz range where the loss of distinction of unvoiced consonants makes distinction of words rather difficult at times, so a "midrange" and "low-treble" boost might be most beneficial.
The use of the aforementioned "AGC" circuit is also important. With nerve deafness, the available "dynamic" range is simply lost, which means that you will have to compress the quiet to the loud into a much smaller set of dynamics.
While there are many ways to do this, among the simplest and most effective are with a resistive opto-isolator - essentially a CdS cell coupled to an LED, with the CdS cell in the feedback loop of an op-amp.
These devices are described here:
https://en.wikipedia.org/wiki/Resistive_opto-isolator
and a real-world application may be found here:
https://en.wikipedia.org/wiki/Automatic_gain_control
I have used these devices many times and they are fairly cheap and work quite well, being nearly fool-proof! By placing a potentiometer in parallel with the CdS cell you can reduce the MAXIMUM gain that will occur under no-signal conditions while putting a resistor in series with the CdS cell can reduce, to a certain extent, the "compression" factor. In the "Automatic Gain Control" article, one could add a separate op-amp section to the LED, itself, so that it "lit up" under a much lower audio level, allowing the AGC to be triggered "sooner." There are versions of these devices with back-to-back LEDs so that asymmetrical waveforms will trigger these devices on the highest peak, but one could also precede them with a full-wave bridge, or simply wire up an op-amp based full-wave circuit as well.
These resistive opto-isolators are made by Vactec and may be found on the surplus market, but are easily made using LEDs and CdS cells - even dual-color (2-lead) units, sealing the lot in black heat-shrink tubing to shield from extraneous light.
Sure, there are more elegant devices out there to do this
(e.g. a VCA based on an OTA) but this is a very quick, easy and simple circuit to build and implement.
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Again, simply throwing amplification into ones ears to overcome hearing loss without known exactly what one is doing is NOT a good idea, but since I just
know that someone reading this forum is going to do it anyway
(human nature!) I just thought that I'd throw out a few warnings and ideas.