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I would like to build a hearing aid, appreciate any professional advice

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I had some other thoughts on your initial question about how you can build your own. There are other skills and tools that you will need in addition to a schematic diagram. You will need to learn how to make a printed circuit board, how to solder surface mount components, how to measure electrical parameters with meters and oscilloscope. Can you do these things now?
 
Hi RadioRon,

Thanks for your concern.
I used to be an electronics technician.
Yes, I can do soldering and read simple circuits.
Can't design circuits though.
 
I think you should build it in stages, maybe using kits:
1) Select a power amplifier circuit that can drive one 32 ohms earbud. A second amplifier and earbud can be added later for stereo. Your brain can use stereo to cancel background noise and echoes.
2) Make a microphone preamp circuit.
3) Try an audio tone controls circuit with bass and treble boost and cut.
4) Try an audio compressor circuit.
5) Try an audio equalizer circuit with maybe 5 to 8 bands of frequencies.

If low frequencies from traffic or air conditioning are bothersome then add a filter to reduce their levels.
 
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I built myself a hearing aid using 2 small ICs. I like ICs because they use minimum external parts this keeps the project small and cheap. Down side is my battery is not small but it will last for months compared to those tiny over priced hearing aid batteries. You can use a larger battery on any hearing aid project.

I learned something very interesting. I have a high frequency hearing loss. I try to watch TV I can hear people talking but it sounds like a bunch of noise. By the time the sound travels from the TV across the room 20 feet to me all the high frequency is gone. Words are missing all the following sounds, S, F, ph, T, etc. The word school sounds like hool to me. Fork sounds like ork. Sky sounds like eye. Flush sounds like uh. I bought a 30 foot long wire on ebay to plug into the TV. Wire runs across the room to the ear phone I use. I can hear sounds I have not heard in 35 years. I can watch TV again. I have tried several ear phones some are better than others. At the moment I am using the free ear phones I got when I boarded and airline from TN to AZ. These are working good for me they look like foam ear plugs with wires but several other ear phones work very well too.

I learned that an ear phone that works good for TV works good on my home made hearing aid too.

Watch this music video. If I watch this using the computer speakers it sounds really bad. I have a good set of speakers with tone controls and it still sounds bad. My son says the speakers sound good to him. If I watch the music video using ear phones WOW I can hear all the sounds. AMAZING. People that have good hearing just don't have a clue what people like us hear.

https://www.youtube.com/watch?v=raDH-CiSXUY
 
Many TV programs play "hide the microphone" game, the news anchors especially. Then the mic is far from the mouth where the high frequency sounds in speech (consonants) are produced then the sound is very muffled (the mic is mechanically muffled). Maybe the mic is under a sweater under the chin instead of in front of the mouth.

I think some videos on You Tube cut some but not all high audio frequencies. The video you posted has too much audio distortion to hear it clearly anyway. What is the language?

Here is a recent American song that sounds almost the same on my pc speakers as it does on a good FM radio:
Recently I watched the live music awards show on TV and it is amazing how many singers CANNOT SING A DAMN without electronics correcting their vocal frequencies (pitch). This singer Ariana Grande sings pretty well but I heard her miss one note in this recording but when live in the show she did it fine. A few years ago the singers played their touched-up the recording and mouthed the words without singing live.
 
The audio opamp is excellent but its minimum total supply is 5V. Many of its features increase its supply current. Many of the features are not needed in a hearing aid so the battery can be smaller if a lower current opamp is used.
The earbuds have NO detailed specs. They "respond" from 20Hz to 23kHz but how extreme are the peaks and nulls or how flat is the frequency response? I could not find their datasheet on Maxell's complicated website. They are cheap so maybe they do not have a detailed datasheet.
 
I was thinking maybe a Lipo battery for longer life and a smaller package.
99, do you have a Lipo charger by chance?
Do you have a cost target?

AG,

How about this compressor?

I've seen a lot of requests for this. It could be a fun project. :woot:
 

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Not much in the way of specs for any of them as far as charts & graphs.
Some golden ear people liked these.

**broken link removed**
 
I was thinking maybe a Lipo battery for longer life and a smaller package.
99, do you have a Lipo charger by chance?
Do you have a cost target?
My radio controlled model airplanes and infrared controlled model helicopters use small Li-Po rechargeable batteries. They are inexpensive and an inexpensive USB charger is made for them.

AG, how about this compressor?
A Jfet attenuator produces severe odd harmonics distortion when its input level is more than about only 100mV. The distortion is reduced and the input level can be much higher if half the signal level at the drain pin is fed to the gate pin. If a coupling capacitor is used to feed the gate pin then its slow charging time slows down the attack time of the compressor.
Here is a link to a good compressor circuit: **broken link removed**
 
OK, and how about this for tone control?
It has 3 frequency bands which is better than only 2 bands. It has the opamp inputs biased at 0V so it needs a dual-polarity supply but the opamps can simply be biased at half the supply voltage then a single supply can be used. The circuit will work with many other opamps with no changes. The circuit is very old so the 5uF input capacitor value is HUGE and the input resistor value is very low at only 10k ohms. The number "5" is not used anymore 4.7uF is used today). Instead I would use 0.33uF (a 330nF film capacitor) and a 100k input resistor.
 
Just add a microphone and preamp to it and do some coding.

Right, just a couple of lines of code. :wideyed:

And here I am trying to find a thru hole headphone driver and you have him doing a 48 pin flat pack.
:)
 
A few years ago there were at least 76 audio amplifier ICs for cars. Now most are gone.
 
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