How to use sound scanner to track a particular frequency?

[electron_boy]

hi
im doing a robot for a competition where ive to constantly monitor a fixed freq sound source and ive to move towards it. so iam using 2 mics for stereo reception of the sound and determining the location of the sound source from the difference of the two mics.im using the following setup

mic-->amp-->lpf-->adc--> difference <--adc <--lpf <--amp <--mic

will the set up work and how to track a particular frequency.probably how much gain should i fix so as to sense the difference in the signals.

 

[XNOX_Rambo]

circuit for sound scanner

I doubt that you will be able to measure any amplitude difference. Instead you
should make use of the phase difference.

I would solve the problem with analogue circuitry and not use ADCs - they add
unnecessary complexity to the design.

/Rambo

 

[Teddy]

sound scanner circuit

A) I do not have any experience
b) - I do not believe you would be able to measure amplitude difference because the source and both mics will be relatively very close to each other.
c) If the mics would be further apart you could measure phase shift difference and evaluate it. But again mics are too close to each other.
d) the best guess right now would be to use very narrowly oriented mic( specialized mic or mic at the end of pipe with sound insulation) - then you would be able to scan the area and in case you get signal to move towards it. since mic would have narrow angle of reception it could work. and you would be able to sense the amplitude just by current comming out from mic and simple comparator.
e) another way could be a simple DLL /PLL kinda architecture - if you know the frequency you can generate it internaly and compare the phase difference of those two. You can "remember" the starting value and use it as reference if you are getting closer or away.... kinda doppler....

 

[flatulent]

Re: sound scanner

You can use the method found in monopulse RADAR. Put the microphones to a circuit that takes the sum to one output and the difference to another. Then compare the phase of the sum and difference. You will get different polarity of phase shift on right and left off axis. If the sound source is straight ahead the difference path will have a very low amplitude signal.

The two microphones should be far apart but not more than a half sonic wave length.

 

[electron_boy]

Re: sound scanner

I doubt that you will be able to measure any amplitude difference. Instead you
should make use of the phase difference.

I would solve the problem with analogue circuitry and not use ADCs - they add
unnecessary complexity to the design.

/Rambo

how to detect the phase difference. can i use the the differential input phase differentiator part of lm565 which is readily available to me right now. because the time is toooooooooo short. ive to present it on 26th feb

 

[XNOX_Rambo]

Re: sound scanner

The answer by Flatulent gives you all the information you need to get you going.

If you want to find out more I suggest you use Google and search using the words
"robot phase direction sound". You may throw in "lego" also... :wink:

/Rambo

 

[electron_boy]

Re: sound scanner

You can use the method found in monopulse RADAR. Put the microphones to a circuit that takes the sum to one output and the difference to another. Then compare the phase of the sum and difference. You will get different polarity of phase shift on right and left off axis. If the sound source is straight ahead the difference path will have a very low amplitude signal.

The two microphones should be far apart but not more than a half sonic wave length.

i think u mean a summing and differential pairs are then connected to the two inputs of a phase detector. then how can the direction be determined. can u please explain or give some links
plz