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Thread: microphone filters

  1. #1
    smkymicpot Newbie
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    Default microphone filters

    Hi can anyone help me?

    I am looking for microphone filters which will filter out souds of close frequencies ( in and around 250 to 500 hz apart).
    so i can play a note of frequency 261 and a note of frequency 400 and the output of the microphone will cause different output voltages?


  2. #2
    Super Moderator Nigel Goodwin Excellent Nigel Goodwin Excellent Nigel Goodwin Excellent Nigel Goodwin Excellent Nigel Goodwin Excellent Nigel Goodwin Excellent Nigel Goodwin Excellent Nigel Goodwin Excellent Nigel Goodwin Excellent Nigel Goodwin Excellent Nigel Goodwin Excellent
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    So you're looking for a frequency to voltage converter?.

    As always with these kind of vague requests, you would do a LOT better telling us EXACTLY what you're trying to do (and why).
    Last edited by Nigel Goodwin; 5th March 2009 at 05:41 PM.
    PIC programmer software, and PIC Tutorials at:
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  3. #3
    smkymicpot Newbie
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    Ok the exact project i am working on is a car which when detects a frequency which i choose, using the microphone filter, causes the car to move forward and when a different frequency is detected, one that i have also chosen, the car will begin to move backwards. the frequencies must be close together as i had intended to be able to control the car by my voice. is it possible to get filters cheaply which will do this? I couldnt find much on filters and am not even sure where to look.

  4. #4
    flat5 Excellent flat5 Excellent flat5 Excellent flat5 Excellent flat5 Excellent flat5 Excellent
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    Why a microphone? You can use dual tone encoders and decoders.

  5. #5
    duffy Excellent duffy Excellent duffy Excellent duffy Excellent duffy Excellent duffy Excellent
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    He said voice.

    smkymicpot - check out an LM567 phase-locked-loop. It detects a particular frequency, you would use 2 of them, one for 261hz and the other for the 400hz signal.

  6. #6
    audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent
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    I am not a singer but I tried singing as high as I can. 305Hz. If I am kicked between my legs then I might scream as high as 350Hz.
    There is no way that I can sing as high as 400Hz. Some "guy" singers can.
    Uncle $crooge

  7. #7
    duffy Excellent duffy Excellent duffy Excellent duffy Excellent duffy Excellent duffy Excellent
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    No, but you can whistle that high. First time I saw a system like this it was in a robotics book by Frank Dacosta, he was whistling in binary.

  8. #8
    audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent audioguru Excellent
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    I studied music every day at home and in school. I almost got "perfect pitch" where a person can identify a frequency like color is to vision. Not anymore.
    Uncle $crooge

  9. #9
    smkymicpot Newbie
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    Thanks duffy I think thatl work cheers 4 d help!!!

  10. #10
    duffy Excellent duffy Excellent duffy Excellent duffy Excellent duffy Excellent duffy Excellent
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    Sure. If you can find a copy of _How to Build Your Own Working Robot Pet_ by Frank DaCosta, it has circuits and code that might be helpful on that.

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