Hearing Aids

Im not 100% sure but I think the Induction loop is used to broadcast sound to hearing aid users from say a speaker using a microphone. maybe telephones too?

As for digital processing I heard this is claimed to allow much larger volume amplification by dynamicaly altering the response to avoid feedback noises. Im not sure if the technology even exists to distinguish wanted noises from unwanted ones.

Colin =^.^=

I know next to nothing about hearing impairments, but I'm fairly certain that in many cases deafness occurs only over specific frequency range(s). That is, the hearing loss is not just a "flat line" attenuation, but is a significant function of frequency. As such, it's much easier to create an "inverse" gain response with digital techniques that it is with analog.

That's pretty subjective. Radio operators use electronic filters all the time to improve signal intelligibility, and although the "noise" coming over a radio has a different distribution than the noise at a cocktail party, it's not much of a leap to suggest that having the ability to filter a signal in ways other than those that your brain alone provides is useful.

I'm not certain, but besides providing power to an implanted receiver, I would venture that it probably also transmits the audio itself.

---Joel Kolstad

Incorrect. The aid should amplify only those sound frequencies which the ear is not hearing normally. Deafness is usually not a "linear" problem, high frequency loss is common. Different patients may cut off at different frequencies. A modern hearing test involves first plotting the response of the ear across the whole of the normal audio spectrum. A modern digital aid is then programmed by computer to amplify frequencies where the ears respose is abnormally low. It therefore is customisable for the individual patient. Indeed a frequency plot and programming is done for each ear, left and right sides may vary for the same patient. If you amplify all frequencies equally you will just confuse the picture. My son for example has severe high frequency loss, but normal low frequency hearing, straight amplification of everything would not be a good thing in this situation. Older analogue aids did have a configurable frequency response curve, but it was not so customisable as with the digital aids and computer s/w.

Harder not easier though if you are being deafened by loud and unneccesarily amplified low frequencies which the ear hears normally.

Induction loops are a method of directly coupling audio to the aid, hence avoiding the listener having potentially confusing background sounds also amplified. Cinemas for example can transmit sound this way if so equiped. Also telephones, whatever. The aid has a "T" switch on it which switches over from normal microphone to loop input.

Steve

Hello Colin,

Sometimes both, power transfer and signal transfer.

It does. There are filter algorithms and slopes that are next to impossible in the analog world. It's tough to say that as an analog guy but that's the way it is. Depending on the case and severity of hearing loss such filtering must be quite intense. Also, it is much better programmable for a custom solution than analog. Some applications such as cochlear implants would be almost impossible in an analog fashion.

Then there are costly component tolerance issues which are eliminated in a digital design.

Regards, Joerg

Hello Steve,

Is there a standard? This would be good for places like our church. We have a radio wand system but have to hand out analog wands that just feature a simple volume control. Plus they break all the time. I've got one here right now where the potmeter became erratic. Again.

Regards, Joerg

"Potmeter"?? What are you smoking at that church ?:-)

...Jim Thompson

Hello Jim,

ROFL!

Ok, yes, we are in California but it doesn't go that far...

It's a drag. Much of that "professional" gear is easily repairable yet often they won't ship you parts or require to send it in to a 'certified repair facility', meaning lotsa $$$. We could somehow find that potmeter but I bet then we'd have to do a minimum buy of a whole crate.

Regards, Joerg

Yes there does seem to be a standard, don't know the official name for it. See the URL below. Places of worship are mentioned in the FAQ here as a suitable application for the technology. There is a standard symbol which can be displayed at sites where T loop is available, which you might recognise, see:

Steve

Hello John,

Hmm, never heard that before. Then again, I didn't grow up in CA. And I didn't grow anything either :-)

IIRC he signed off a while ago because of some job, I think. But it's been a while.

Regards, Joerg

Hello Steve,

Interesting, thanks! I had asked a few of our hearing impaired and none had ever heard about such a system. Looks like it would be around $2k for our size church if we do the install as volunteers. That's more than the existing system but considering the convenience it would make sense. As long as I can find out whether the majority has T-Loop enabled hearing aids.

Regards, Joerg

dunno, miss his wit, He's one of the good guys here, along with Win and Jim (ooops)

martin

I have seen his cross-posts from sci.lang.translation recently, so it wasn't entirely work-related...

Best regards, Spehro Pefhany

Well! There certainly hasn't been any requests for serious circuit design help here in a very long time, so I guess I'll have to just keep picking on leftist weenies :-(

...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

We're hoping you're going to start writing that book of yours, Jim. :-)

Keep me loaded up with "exercises" and I'll start writing. Writing, by itself, is terribly boring... after all it's an "I did that already" task.

Reminds me, my wife is very active in charities and Girl Scouts. Nearly 30 years ago I had a sculpted gold pendant made for her....

(o) I DID THAT ALREADY

(Except that "THAT" was properly half-spaced ;-)

...Jim Thompson

Seems as if there is more awareness of T-Loop here locally in the UK. It's common to see the sign in banks for instance, as the teller has to use a microphone to talk accross the security glazing. All the aids son Tom has been supplied with have a T setting. Check out a major player like Siemens if you need more detail on them

Steve