Author Topic: "Hearing Assistant/Aid"  (Read 6883 times)

0 Members and 1 Guest are viewing this topic.

Offline Marco

  • Super Contributor
  • ***
  • Posts: 2397
  • Country: nl
Re: "Hearing Assistant/Aid"
« Reply #25 on: February 11, 2013, 08:11:27 PM »
The pure in ear devices are justifiably expensive ... they are also highly unoptimal.

Necklace worn microphones offer far superior information for source separation filters ... and avoid the need of trying to get all the DSP hardware into a tiny in ear device. Getting stuff like voice detection and blind source separation right though seems non trivial.
« Last Edit: February 11, 2013, 08:16:53 PM by Marco »
 

HLA-27b

  • Guest
Re: "Hearing Assistant/Aid"
« Reply #26 on: February 12, 2013, 01:15:30 AM »
Can someone point to some reading material about the nature of the signal processing that needs to be done?

For example when we are talking about hearing damage are we talking about decreased sensitivity across the bandwidth of for example loss of hearing in a certain part of the bandwidth?

Besides the standard LP HP and BP filters, do we need to consider compressors? For example if the person's hearing only works between 200 - 600 Hz do we need to compress the entire spectrum to this particular range or do we just apply filtering? Hell I don't even know if this selective bandwidth thing even exists..?
 

Offline shaddai

  • Newbie
  • Posts: 4
Re: "Hearing Assistant/Aid"
« Reply #27 on: February 12, 2013, 07:40:03 AM »
Quote
Can someone point to some reading material about the nature of the signal processing that needs to be done?
Do you mean how DSP works, or what should happen in the 'real' analog world of creating clarity of sound for your ears?

Quote
do we need to consider compressors? For example if the person's hearing only works between 200 - 600 Hz do we need to compress the entire spectrum to this particular range or do we just apply filtering?
Compressors compress dynamic range..ie: turn loud things down in a very fast manner...like reshaping the sound of a snare drum hit, or leveling out volume between bass guitar notes. I'd imagine this is precisely what you wouldn't want to do with hearing assistance because it could kill off the clarity of consonants. Now, an expander + a limiter, that might be useful to make consonants louder & then limit them to a max loudness.

Moving a 2000hz sound down to a 200hz sound is pitch shifting. It's typically kinda mucky & bizarre sounding if you're being that aggressive with it.

Quote
Hell I don't even know if this selective bandwidth thing even exists..?

Seems to me you could hook a microphone to preliminary HP/LP/BP filters, then split the signal to a super snappy VCA chip, and send the rest of it to a dsPic/blackfin/whatever running an FFT routine or something like that. Once the dsPic deciphers sounds from 2khz-4khz, use it's DA converter to juice the gain on a VCA. Use that with some open air earbuds & only amplify the frequency range that needs to be amplified, and only when it is present. The whole board could be 2-3 chips + some passive components. Might even get someone to make a windows gui to write amplification behavior tables to the dsPic.

Just a thought.

todd 

 

HLA-27b

  • Guest
Re: "Hearing Assistant/Aid"
« Reply #28 on: February 12, 2013, 08:52:57 AM »
Quote
Can someone point to some reading material about the nature of the signal processing that needs to be done?
Do you mean how DSP works, or what should happen in the 'real' analog world of creating clarity of sound for your ears?

I mean medical studies on patients. It wasn't very clear I confess.

For example we need to know if some hearing deficiencies are frequency dependent. If a patient who has lost most of his hearing can retain some of it in a certain frequency range. Then we need to know whether it is useful or not to remap normal speech frequencies to this patient's hearing pattern. Can a patient get used to it and start to recognize speech better? Or maybe it has side effects? Wrong glasses can cause headache and nausea, how about wrong hearing aids?

All in all, I'd rather read some medical research instead of going on intuition alone.
 

Offline shaddai

  • Newbie
  • Posts: 4
Re: "Hearing Assistant/Aid"
« Reply #29 on: February 12, 2013, 09:04:43 AM »
Gotcha.
 

Offline jeroen74

  • Frequent Contributor
  • **
  • Posts: 395
  • Country: nl
Re: "Hearing Assistant/Aid"
« Reply #30 on: February 12, 2013, 09:11:19 AM »
Quote
Can a patient get used to it and start to recognize speech better? Or maybe it has side effects? Wrong glasses can cause headache and nausea, how about wrong hearing aids?

My daughter has cochlear implants (direct electrical stimulation of the auditory nerves) and this sounds highly unnatural; everyone sounds like a Cylon . This does not cause nausea or headaches. At most it can be tiresome.
 

Offline qno

  • Frequent Contributor
  • **
  • Posts: 407
  • Country: nl
Re: "Hearing Assistant/Aid"
« Reply #31 on: February 13, 2013, 02:44:06 AM »
Hi all,

Some ideas:
Years back i saw some studies with multiple microphone array's that gave a directional effect.
Spacing between the mic's would attenuate specific frequencies and amplify others.

A hearing problem does not always mean the absolute sound level hearing.
One can have a good conversation in a quiet room but as soon as environment sounds at specific frequencies appear following the conversation becomes a problem.
I have anticipated in some test where a tape was played with a newsreader at a normal conversation level.
Then the same tape was played but white noise was added until the signal noise ratio was 3 dB.
Very quickly the newreaders voice was difficult to follow.

I had a friend who was a shortwave radio HAM. He could pick up HAM conversations burried in noise where I could hardly discriminate a calling station. This was training the brain to do the DSP.
I admire people who can have a conversation in a Disco or on a factory floor with heavy equipment.
Altough i think they do more lipreading than hearing.

Understand that when you amplify sound it also amplifies the unwanted surrounding noise.
The trick is to discriminate those 2 and only amplify the sound you want.
The easiest way to do this is make the distance to the sound you want to hear short and the distance to the noise large.
If you decouple the mic from the earpiece and point it to your subject you will do better that fancy DSP algorithms.

Hide your micophone in a ring or watch and you can bring it discretely to the subject.
Maybe a bluetooth earpiece with some bluetooth   microphones will get you going.

Using both ears and 2 channel audio will give a stereo image in your head. This will make it easier for the brain to conentrate on a single voice in the stereo image.


Why spend money I don't have on things I don't need to impress people I don't like?
 

Offline jeroen74

  • Frequent Contributor
  • **
  • Posts: 395
  • Country: nl
Re: "Hearing Assistant/Aid"
« Reply #32 on: February 13, 2013, 02:55:26 AM »
I think no algorithm has been invented or found yet that can separate one voice from background noise like the human brain can. There's more then just simple frequency domain filtering as multiple voices occupy the same frequency band.
 

Offline Marco

  • Super Contributor
  • ***
  • Posts: 2397
  • Country: nl
Re: "Hearing Assistant/Aid"
« Reply #33 on: February 13, 2013, 03:50:16 AM »
With multiple microphones you can isolate sources. ICA is a famous algorithm for this for instance, but requires as many microphones as sources I think so is not the most practical one.
 

Online mswhin63

  • Frequent Contributor
  • **
  • Posts: 323
  • Country: au
Re: "Hearing Assistant/Aid"
« Reply #34 on: February 13, 2013, 12:00:22 PM »
I run an assistive device business in Australia and experienced in many aspect of hearing loss. The issue with any electronic device is that the product is only as good as the weakest link.

In a hearing aid the weakest link is the microphone. It is so damn small. For any of the initiated compare a large dynamic microphone with a lectern microphone on a podium. You can shove a microphone directly into your mouth and still get a good sound while the podium microphone always gets up peoples noses when they do not know how to talk into them.

Physic dictates the size of the diaphragm will naturally resonate at higher frequencies based on smaller sizes. Filtering is the only way to deal with this but the hearing aid is  such a small device that it is hard to place good filter whereas body aids are easier. This is why many people including my wife love the older larger hearing aids.

Enough said I am going back to Uni to study Electronic Engineering as I am only a lowly Technician and I have a idea that after listening to Dave may make it open source the main idea is to deal with the microphone in a way to avoid recognition and allow people to wear the device in confidence. It involves my wife and her excellent crafting capability as well. It maybe so simple that I may just use it to gain my experience in Science and engineering and give it away.

For a minor plug not my website but my suppliers website these products from Bellman are the best I have provided in a long time. There are so many other alternatives around but performance is not as good. Unfortunately market power dictate these to be quite costly. www.bellman.se/audio
YouTube Channel: https://www.youtube.com/user/astrelect

Half a century later and I finally studying.
 

Offline NiHaoMike

  • Super Contributor
  • ***
  • Posts: 2890
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
Re: "Hearing Assistant/Aid"
« Reply #35 on: February 15, 2013, 05:10:33 AM »
Apart from the obvious voice band filtering, you could use directional microphones aimed to give the highest sensitivity at typical conversation distances.

Online mswhin63

  • Frequent Contributor
  • **
  • Posts: 323
  • Country: au
Re: "Hearing Assistant/Aid"
« Reply #36 on: February 15, 2013, 08:50:06 PM »
Apart from the obvious voice band filtering, you could use directional microphones aimed to give the highest sensitivity at typical conversation distances.

There are already hearing aids available with voice band filters and up to 6 microphones in some instances but way out of the price range of most people with hearing loss. Some of my former clients purchased $6 - 10,000 per hearing aid to achieve this and what concerns me about the practicality is why did they come and see me in the first place.
YouTube Channel: https://www.youtube.com/user/astrelect

Half a century later and I finally studying.
 

Offline NiHaoMike

  • Super Contributor
  • ***
  • Posts: 2890
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
Re: "Hearing Assistant/Aid"
« Reply #37 on: February 16, 2013, 05:29:15 PM »
How difficult is it to create a cheap open source version? Fast ARM boards like the Raspberry Pi are quite cheap nowadays.

Offline Marco

  • Super Contributor
  • ***
  • Posts: 2397
  • Country: nl
Re: "Hearing Assistant/Aid"
« Reply #38 on: February 16, 2013, 10:54:54 PM »
Most of the cost is in the non recurring part ... ie. find someone mad enough to actually do it and not charge for his time.

Also if you try to use advanced signal processing with multiple microphones for voice isolation or frequency compression I expect a contributory infringement lawsuit, so better not publish under your real name.
 

Offline jeroen74

  • Frequent Contributor
  • **
  • Posts: 395
  • Country: nl
Re: "Hearing Assistant/Aid"
« Reply #39 on: February 17, 2013, 12:30:26 AM »
As a practical note.... my daughter goes to a regular school and to help her hear the teacher better, the teacher wears a wireless microphone. My girl wears a receiver that retransmits the received signal to the hearing aids via a standard inductive ring? interface.

So even with four DSP cores they can't even begin to come close to the processing capabilities of the human brain, which after all, just has two microphones as input ;)

IIRC these hearing aids already have two microphones to help voice separation, one omnidirectional one and a unidirectional one. The algorithms is what sets the four different manufacturers apart, but they all function about just as good. It's subject of major marketing blahblah.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf