pick up voice from 3 meter away, electret microphone

Discussion in 'General Electronics Chat' started by bug13, Jan 30, 2015.

  1. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
    38
    Hi guys

    I want to be able to pick up human voice/speech from 3 meter away, can I do that with an electret microphone? what specs should I be looking for in a datasheet?

    Or if not practical to use an electret microphone, what else can I use?

    Thanks guys!!
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,281
    1,232
    Sure.
    If I remember the numbers right a wm61 is a good one.
    you will need to amplify it as they put out very low voltage (mv).
    Edit: Part number
     
    bug13 likes this.
  3. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    bug13 likes this.
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,986
    3,726
    @bug13
    Even a cheap electret will work. I was trying to build a small, high gain, low noise microphone circuit and used all low noise components yet I still had a hiss. I changed everything. I even tested if I could make the noise louder with a cheap electret from RadioShack. The noise was the same. It turned out to be the refrigerator motor 4-meters away. Voice at 3-meters will be fine.
     
    bug13 likes this.
  5. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    Years ago I built a very high gain electret booster with a TL431 programmable zener - its not exactly Hi-Fi, but perfectly adequate for speech.

    For a 5V rail; start with 2k2 from cathode to Vcc, put the mic from sense to GND, hook a 47k pot from K to sense and adjust the output quiescent point - don't forget that K can't swing lower than about 2V. Once you've determined the bias resistance, hang a 1k2 resistor from K and shunt the other end of the resistor to GND with a 100uF cap, take the bias resistor from the top of the cap to the sense input.

    If it picks up local radio - put some resistance in series with the capacitor.
     
    bug13 likes this.
  6. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,281
    1,232
    TL431.. Neat part.
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    My very first prototype of that project was with an 80 Ohm speaker and 12V Vcc.

    Once I'd included the 100uF capacitor to shunt AC nfb out of the DC nfb that stabilises the operating point - the only way I could prevent howlround was with the mic on a length of twisted pair and placed in another room.

    With 12v and such a low Ohm load, the TL431 ran uncomfortably warm, but I'd proven the point and quickly devised a power MOSFET stage to follow it.
     
  8. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    Do I miss something or you type the wrong word → make the noise louder, why you do that ?
     
  9. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    8 ohms or 80 ohms?
    I bought an indoor intercom system long time ago, they used an 8 ohms speaker to replaced the mic, but I can heard the voice from another intercom very clear, even my wife far from the speaker about 100 cm, the speaker still can pick up the voice easily, so I think the amplifier is very important.
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    8 Ohms would be a bit stiff for a chip in a TO92 package running off 12V.
     
  11. Rocket.Man

    New Member

    Jan 1, 2012
    20
    7
    Picking up sound from 3 meters away is not hard. 35 years ago I built a big ear I experemented with several mics then finally after lots of experements I learned an 8" diameter speaker is extremely sensitive to very small sounds I am able to hear people talking 1/4 mile away. I built a 2 IC op amp, both ICs have a gain of 200 with a volume control on both amps.

    http://www.talkingelectronics.com/projects/HearingAid-2/HearingAid-2.html
     
    bug13 likes this.
  12. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
    38
    Thanks a lot guys, thank you for all the inputs, I believe my problem is solved!!
     
Loading...