Need info on filtering audio

Discussion in 'The Projects Forum' started by yaantey, Oct 9, 2011.

  1. yaantey

    Thread Starter Member

    Oct 7, 2011
    I am capturing a audio (baby's voice) with a mic. And I want to send it to micro-controller and then transmit it to a receiver wirelessly. So, I would like to know if I need to amplify the baby's voice and filter it in order to cancel out the background noise (it is a must to cancel out any background noise as much as possible).
  2. bertus


    Apr 5, 2008

    In the old days, the phonecompanies used a bandpass filter from 300 to 3000 Hz to filter the human voice, in their analog phone systems..
    The below 300 Hz reduces the humm and above the 3000 Hz reduces the hiss sounds.

  3. iONic

    AAC Fanatic!

    Nov 16, 2007
    As we are talking about a baby's voice the following may not apply here, but is useful information for other that might consider a similar filter for the adult population.

    From Wikipedia:
    The voiced speech of a typical adult male will have a fundamental frequency from 85 to 180 Hz, and that of a typical adult female from 165 to 255 Hz.[1][2] Thus, the fundamental frequency of most speech falls below the bottom of the "voice frequency" band as defined above. However, enough of the harmonic series will be present for the missing fundamental to create the impression of hearing the fundamental tone.

    A typical baby's voice freq. is about 400Hz, a distressful cry......probably about 20kHz!!!!! Just kidding on the crying freq.
  4. #12


    Nov 30, 2010
    Second time today...use 2 microphones wired in opposition so they cancel far field noises. Then amplify the result. Building the amplifier is a perfect opportunity to limit the bandpass frequencies.