Geophone amplifier

D

dlwilliams

New Member
My son has one of thoose Foot stomp detectors with led lights, built from a kit. Now he wants to listen to this using a speaker. So he can hear his mother walking up the sidewalk.

I hooked it directly up to a mini amplifier but this does not work.
Then I notiece that it is a 10hz geophone transducer. We cannot hear that low so I am taking a guess that this need to be shifted or somthing like that.

I haven't a clue as to how to accomplish this or what I am doing.

Do anybody care to help with this.
 
You are correct, 10Hz is infrasonic and we can't hear it.

You could turn the volume way up so it clips and generates loads of audiable harmonics.
 
Like I said you want to clip the waveform which will generate harmonics which you can hear. You can do this by amplifing it to around 2V peak to peak and adding two diodes in reverse parallel. It'll sound like lots of clicking noises or a buzzing sound.
 
I want to hear the actual sound not loads of audiable harmonics.

I thought there was a way to take low freq. (5-20hz) and multiplex then up to 205-220hz (for example) so I could then amplify them by say 2 watts and listen to it with a speaker or headphone.
 
I found everything very interesting.
However, I know little about electronics and I sould have been a little more forward about what I was looking for.

I am looking for sombody that would like to build such a schematic for a price or not.
 
Yes it is but the problem is that it's hard for the ear to differentiate between 205Hz and 220Hz.

If you took the 9th harmonic of your 5Hz to 20Hz infrasound if would become 45Hz to 180Hz which is much easier for the ear to differentiate between.

Another option would be to record it and speed it up, there are digital techniques that can do this on the fly but they're not easy to do. The only good thing here is that not as much processing power is required at these extremely low frequencies.
 
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