DIY ALD from off the shelf parts

I think its possible to create not only a very competitive ALD (assisitive listening device), but also a hearing aid system from off the shelf parts as well. In other words you make your own system. I believe a simple system can now be built by people that are not electrical engineers or similar.

I think a parts list could be assembeled such that even non tech people can purchase and use.

Rough estimates - good hearing aids run about $3000 each. A device like a Zoomlink runs about $1500. So thats roughly $7500 for a system that will be obsolete in 2 or 3 years.

I think we should attempt to make something simple to give people an option. Maybe this will fizzle out to nothing, or maybe it will take off and be useful and developed, or maybe its already been done by others a thousand times I dont know.

I got inspired my what Musick7 did, except it looks like he is high tech capable, I am not so much. Also he is doing the processing inside his hearing aid which is a principal I dont want to follow. I want the processing done outside the hearing aids to free the hearing system from the #1 bottleneck and limitation of hearing aids -Processing power which which is limited by available battery power.

I would like to start very simple and follow the KISS design idea (keep it simple stupid). Its possible that even trying to build a very simple system involves problems that will essentially impossible for the layman to oversome.

I would be nice if others would buy the parts too, utilizing the ideas here or thier own ideas, but at least provide your gained knowledge here for others to benefit from. I purchasd some items on Amazon last night and they are being shipped out. Its my attempt to piece together a very simple starting system that uses bluetooth, cost so far is $128. Many of these parts can be used for other things so service a dual purpose which is nice. I have to run now but will be back later today.

Some very good information on what bluetooth is at wikipedia at


Its a technology that I have ignored for years and know little about. It sure has developed alot though recently and has become much cheaeper.

I am looking at this as being two problems, a software problem and a hardware problem. To me the software problem is where I want to get to, where all of the potential is. I envision geting to the point where I use a PDA or similar with small usb sound cards attached to process the sound, then cheap class 1 usb bluetooth dongles attached to transmit sound to class 2 or class 3 bluetooth recievers in the hearing buds. The hearing buds will look identical to a BTE hearing aid as a final goal, with the mold and the casing simply purchased from some source.

quick review on bluetooth

ClassMaximum Permitted Power
mW (dBm)Range
(approximate)Class 1100 mW (20 dBm)~100 metresClass 22.5 mW (4 dBm)~22 metresClass 31 mW (0 dBm)~6 metres

ClassMaximum Permitted Power
mW (dBm)Range
(approximate)Class 1100 mW (20 dBm)~100 metresClass 22.5 mW (4 dBm)~22 metresClass 31 mW (0 dBm)~6 metres

Latency is an issue with bluetooth, I think what that means is that there is a delay between the mic getting the sound and what you hear. Thats way beyond my scope right now so I will ignore it but it could end the project as well as many other issues.

My first goal and to assemble a simple wireless microphone speaker system. In fact I am going simpler than that. The first goal is simply a wireless mic that transmits sound via bluetooth to a usb bluetooth reciever attached to my pc. If I can succeed there great then I can move on to the next step. It seems like it should be a simple thing but you never know.

I tried to get a class one (320 ft range) bluetooth transmitter that was portable, I cannot find this nor do I know if it would be considered safe to wear this powerful of a transmitter around your neck. I think what I ordered was a class 2 with a 33 ft range, good enough for now. Here are the parts I have so far:

100m Wireless Bluetooth USB Dongle for PDA/PC/cellphone
Kinamax BT-USB Wireless Bluetooth 2.4Ghz 100-Meter USB 2.0 Dongle Class 1 External Adapter
Cyber-Blue Bluetooth v2.0 EDR USB Dongle Class 1
Tiny Bluetooth USB Adapter Dongle (Black)
Sony Bluetooth Wireless Stereo Transmitter (Model# TMR-BT10A
3.5mm Wireless Bluetooth Stereo Audio Dongle Adapter for CD/DVD Players MP3 MP4 PC PDAs iPod PSP any 3.5mm Jack Devic
Jensen WBT210 Bluetooth Portable Universal Stereo Receiver with Intergrated Microphone

Some problems that immedietly come to mind. I doubt the bluetooth transmitter’s 3.5 plug will provide phantom power for a microphone. If not I have some self powered mics. I think being able to use any mic you want is critical and full of potential. For example, the pockettalker will not let you use standard mics which is irritating to me.

As can be seen you can get usb bluetooth dongles now for $1.50. I got some of those to see how they work, plus some more expensive class 1.

ClassMaximum Permitted Power
mW (dBm)Range
(approximate)Class 1100 mW (20 dBm)~100 metresClass 22.5 mW (4 dBm)~22 metresClass 31 mW (0 dBm)~6 metres

A prof in texas doing a very similar system

I have purchased an I-pod touch which is similar to the I-Phone but doesn’t have a cell phone. There are hundreds of thousands of applications that can run on the touch. I purchased one for $9.99 called “Sound Amp”. It basically turns my I-Pod into an ALD. Since the Touch doesn’t have a a microphone, you have to use a mic/headphone plugged into the 3.5mm headphone jack. There is one mic/headphone combo called “monster” that separates the mic from the headphone part and gives you about 30 inches to place the very strong mic on a table for example (I attach the mic to a fork and set it in the middle of the table at a restaurant or meeting. The Sound Amp program has several settings, one is flat, and the other three increase the higher frequencies in different configurations. I find the flat to sound the best. I can use it without my hearing aids. I know some people who have used ear buds with their CIC and also get good results. I haven’t tried it with my I-com because the earbuds are good enough for me. I’ve tried it with bluetooth headphones but the software cant access the bluetooth on the I-Pod…yet. The author of the application is working on that. So, the I-Pod touch costs $199.00, and the mics/headphones are about $25.00 and the software is another $10.00. The Touch is a mini computer with wifi and tons of other cool stuff. This is the future for ALD’s.

That is great to hear. The apple products tend to be very good. I know my wife’s ipod is like indestructable and the sound quality is second to none.

Thier application idea is fantastic where you can get almost any application with more coming. I am planning to get a more generic version of a PDA like thing but the apple products are hard to beat.

I found some really good reading at the prof’s website mentioned at the above link. I enourage anyone to google his name and surf his site.

Awesome article

part 2

Some of these links were really hard to find. Here is one of the best ones…

Once again the Europeans seem to be ahead in like, everything

It turns out that building a simple mic, headset system is very possible, but some basic problems need to be solved. So far I am stuck right at the beginning, learning about bluetooth. It turs out that bluetooth USB is available widely in europe and japan, but not so here yet for some reason, at least not in such a way that it is easily configurable with Windows and other operating systems. I know that licensing fees and greed in general are responsible in a large part to the difficulties people here face in getting these things to work on thier pc for now.

I briefly got one USB adapter to work and will continue.

I recieved my Sony portable bluetooth transmitter with 3.5 mm input and Jensen reciever with 3.5 mm headphone jack. They work very well. The sound quality sounds to me like CD quality, absolutely no noise or hiss, even though the 3.5 mm connection is not ideal (but it is the most flexible). The transmitting range is 10 to 30 feet so far, good enough for now.

I would skim through these links if you are interesting in this subject. The second article is great to me not so much for the speech recognition, but for the fact that it cleans up the sound so well.

Listen to these sound files if you hearing is good enough. Incredible!

I forgot to mention, that I can only spend about 30 minutes a day on this project. So it will it will be slow going. Right now the problem is getting a bluetooth dongle to be recognized by windows and understanding in basic terms how it transmists files and sound.

I wonder if this would be a good solution for the receiving unit for now. It has the speaker, amplifier and bluetooth. Its probably a class 3 bluetooth (6 feet) but thats more than good enough for a body worn PDA. I would need to look into the data rate so that it provides the best sound quality possible.

Just wanted to post an update, I have been mostly reading a few minutes a day from the articles I downloaded. I got a shotgun microphone today from Amazon, adding that to my experiment pile.

Also wanted to mention something about the pocket talker. I called the other day to ask them if I could use other, non standard microphones, they said yes. The pocket talker ultra does provide phantom power, I think its about 5 volts.

My pocket talker has a lip that goes around the mic input that prevents most mic’s from being plugged in, unless you buy it from williams sound. Solved this problem with a dremel and grinded the lip off. The sound quality using some of my mics was very good, however I need to speak closely to the microphone in order for there to be sound.

I will be looking into what types of microphones can be used to pick up things from far away, as well was what types are the most directional.

Check out this interesting product!

Basics of Microphones. Goes on a a few pages, not too difficult to follow. My shotgun microphone arrived. Hooked it up to my Pocket Talker Ulta after getting an XLR to 3.5mm adapter. Wow very nice sound and very driectional to say the least.

Forgot the link

Certainly a cheaper version of personal FM is very easy to do. These little FM transmitters designed to carry music for your car stereo system transmit on any “blank” FM radio frequency. All you then need is a standard FM radio to receive that input and away you go. It doesn’t give you a mic for someone to talk into, but for listening to sound sources the whole thing can be done for about $30 for without hearing aids use or closer to $50 if you want to plug it into a hearing aid direct input. OK so it’s not major engineering and it will still quickly go obsolete, but it’s cheaper than a personal FM!

Thats a great idea for building something quickly and that would be useful. FM defeats the whole purpose of doing this project though since the sound quality is much too variable and poor, even in the best circumstances. Many of the people here who sell them, or someother junk will disagree.

I disagree and I don’t sell anything! I just happen to find that for me personally an FM system is much better than my hearing aids, even though my FM is a £300 model bought in 1995 and the hearing aids are pretty recent. I even prefer the environmental sounds through the FM system, if I am wired into my box anyway then I’ll put in my local monitor mic and use that rather than the hearing aid mics.

The sound zoom is massively superior, if I put the FM transmitter by the TV I cannot hear a single other sound in the room, but the moment I mute the TV it jumps to my husband speaking several feet away without hesitation, then back to 100% focus on the TV. Not what everyone wants, but for me I find the focus on a single sound impeccable compared to my BTEs which give a small level of additional priority to the sound in front but still feed in both sounds, and struggle to work out which sound I am most likely to want to hear between someone typing on a keyboard or someone talking to me! Everyone is different, I guess, and some people can’t stick FM at all. I was told my hearing loss was not bad enough to need it, but they got it for me anyway at school and I’ve been a devoted user ever since.

Now when the day comes that we can send battery power wirelessly we can have some truly awesome hearing systems! :smiley:

I am glad you like your FM system