Electronic Hearing protection

[clueless]

I saw some earphones designed for hearing protection that allow verbal communication ,while blocking equipment noise etc.

I was wondering how difficult it would be to make such a circuit.I'd like to make something like that.
Any help would be appreciated.

 

[Sceptre]

only thing i can see would be a filter of specific frequencies. would not always be reliable depending on who you're talking to or what machinery is in the background

 

[diode]

I think there is alot more then that, I know for example that some mobile phones brands include very sophisticated noise reduction alghorithms, and I have to say I can really hear the difference when speaking with someone who is in a noisy place.

For what I know anyway they are very complicated algorithms, and even proprietary if I recall right.

I just throw my 2 cents, but I have never done anything like this, how about 2 microphones at, for instance, 90 degrees and then make some sort of difference of the two signals? This assumes that one guy is speaking from near and front of you and the noise is more distributed in the ambient (coming from more far) so it would affect in similar level both mics ? Or maybe then not...but could be tested.

 

[crust]

The microphone idea is basically how it is done, though they usually also have some filtering, etc. Most noise reduction headphones also work the same way.

 

[stevez]

There might be a reasonably simple solution. First, you'd select headphones that provide the desired degree of isolation. This might be a trial-and-error kind of process. Next you'd need to select a microphone and amplifier. The microphone would have to be sensitive enough and responsive enough for your needs.

The amplifier could be simple - or more complex depending on your needs. I'd guess that commercially available equipment has gain and compression circuits, as well as filters, noise cancellation, to make the adjustments but that limits the output to safe levels. Any amplifier has limits. You might find that something like an LM386 can't drive your headphones hard enough to be deafening - and in your situation you might be able to get away without compression or automatic gain controls. There might be some tried and tested methods for automatic gain control or compression that are easily applied to a home-brew situation. "Compression" is used on transmitter inputs for amatuer radio -maybe you can borrow something from there if you need.

A brilliant idea just flashed into mind - add a voice recognition circuit that would allow the amplifier to select what audio to pass along or reject. The application I had in mind was the home workshop where my hearing protection provides a get-out-of-jail card when I claim not to hear requests to perform household chores. I could imagine a more compact version for use on Sundays during football games. Thanks for the idea. Only downside that I can see is a loss in the fine art of "tuning out" but there's no such thing as a free lunch.

 

[tansis]

Here's a circuit I found on a trawl of the web last year...
full page at
https://headwize2.powerpill.org/projects/showproj.php?file=noise_prj.htm

Noise-Canceling Headphones by Jules Ryckebusch

 

[clueless]

Thanks for all your help!!

I'm gonna try building the circuit that tansis gave the link to.

Thanks again!