Enhanced hearing

Not going to work.

Your ears can already hear way down low. Problem is in almost any place except the middle of a desert, with no wind, there's a constant background noise level. If you amplify the sound you're just going to bring up the background noise. And you're actually worse off, as your typical microphone and earphone doesnt have the dynamic range of your ear. It's hard to compete with a billion years of evolution.

If you want this to work, you'll need a very directional microphone, like take an old 3-foot fiberglass snow-disk and place the microphone at the focus. Works really well.

I was thinking, maybe an 8" dish cut in half, with one half on each side of his head, their focal points at his ears.

Then I thought, "What a Mickey-Mouse arrangement that would be!" ;-)

Cheers! Rich

Hello,

That was actually part of my question... the specs for the microphone. I've read about others accomplishing this feat using directional microphones, but I don't know much about them. I've also read of other setup where they use a differential input to cancel out the noise, but I also don't know much about them either.

Thanks!

going to work.

They're called "hearing aids".

But as someone points out, when you start amplifying to hear the distant and weak signals, you also amplify the closer and louder signals. So if you want to hear that older guy barely speaking next to you, when you crank up the amplification the frogs in the pond outdoors are far louder.

Of course, hearing aids aren't quite so much about making things loud, as they are about selective amplification, to compensate for hearing loss.

The details of your "bionic ear" really are too micro, they deal with fine detail that ignores the bigger problems.

You've overlooked the selective nature of "stereo" hearing; having two ears really does help to "tune out" the unwanted sounds. The head does help.

And you need to deal with coupling the amplified sound into the ear.

Some sort of selective and variable filtering might be useful, so you can get rid of those obnoxious frogs (though at the expense of a slot in the frequency range for the other sounds). The "Bionic Man" would have it done all with computer, so there is some algorithm to get the sounds you want and get rid of the unwanted sounds without much fussing by the person using it.

Michael

I also read about hearing aids using DSP-based devices that offer selective frequency amplification, but what I really want for now is just some sort of "sound" telescope that can amplify any sound.

Anyway, the application of this device is somewhat silly. I was thinking of creating a tone generator and attaching it to another object. I would throw this object or hide it in the bushes and use the "enhanced hearing" device to detect the location of the tone. It's for some game that I thought about. Of course, if I know the tone's frequency, then I can just use some form of tight bandpass filter to get rid of other frequencies.

Thanks!

Michael Black wrote:

going to work.

martin

If you want to do something more advanced than simple analog circuits, parabolic reflectors and the like to enhance sound, consider using DSP, Digital Signal Processing to accomplish your goals. One thing you could do with DSP is frequency shift so that you can hear bats and ultrasonic insects and other interesting things either above or below the frequency range of human hearing. Another thing is to selectively amplify only certian frequencies or certain sound patterns to increase the aural acuity. Still another is noise shaping and filtering to increase the signal to noise ratio. Furthermore it is possible to do correleation techniques on very weak repetitive signals to pull them out of noise. There's many other neat things that can be done with DSP. If this is for a class or to learn somethng more or less at the state of the art, I suggest you look into it. Bob

...

He should just make a functioning pair of Mickey Mouse ears. ;-)

Cheers! Rich

Think about signal to noise ratio. You want to reject unwanted sounds based both on their frequency and direction to source. If you can characterize the kind of sound you are interested in, there may be additional techniques you can use to select them.

Three. That last one put you over the limit. ;-)

It should also be possible to build a "Yagi" microphone:

A string of microphones spaced an integer wavelength distance. Amplify the signal from each microphone and then add up the waveform with delay lines so the same point on the signal is added to the signal and different signals average out.

The effect is to amplify the signal from one direction.

"Frithiof Andreas Jensen"

....... Phil

"Frithiof Andreas Jensen" wrote in message news:ei7j6m$7jv$ snipped-for-privacy@news.al.sw.ericsson.se...

Wrong term... you're thinking of a phased array, where (at least to a first approximation) radiation/pick-up is modeled as the superposition of each antenna's standalone output/input.

Yagis place the elements close enough together to get significant coupling from one radiator to the next.

Won't work very well. The Yagi is a narrow-band device. That's fine at radio frequencies as often you're just interested in a small band of frequencies, less than 10% wide.

it's a narrow band device because it requires the reception elements to have different phase shifts at the center frequency-- that's how it acts directionally.

But audio freqs span many octaves, much wider than a Yagi can handle.

Plus the dang microphones would have to be on the order of half the audio wavelengths in size-- not too practical below a few KHz.

No, he's not talking about a phased array, he's talking about a Yagi. Or maybe more accurately, a Yagi-analog, or quasi-Yagi. The spacing of the elements is less than .25 wave because of those coupling effects that you've mentioned (in the electrical one), but the effect is the same: A particular wavefront comes along, and hits each mic in turn. Now, the mics don't reradiate, so you'd either put them at 1 wavelength or 1/2, where every second one has its output inverted.

That would be very directional, at one frequency, but the signal would be swamped by ambient noise.

Yesterday or so, I tried to search for the "shotgun microphone" that I saw a construction project on in the '60's - it's composed of a bundle of aluminum tubes, one 36" long in the middle, then in a hexagonal pattern,

I hear that one's not only highly directional, but has enough bandwidth to understand people talking.

Good Luck! Rich

Rather than aluminium I believe fibreglass would be lighter and have some damping. Apparently they are a surprisingly effective directional mic. Also a horn design worked much better than expected.