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Altera_Forum's avatar
Altera_Forum
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16 years ago

Sound amplitude

Hi,

I'm trying to write noise gate in vhdl. I use DE2 board and I wonder how can I compare sound amplitude and threshold in noise gate. How can I check sound amplitude value?

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    In order to estimate the sound amplitude, you can use a modified moving average filter like this:

    y[n]=1/N*sum(k=0,k=N-1,|x[n-k]|)

    This resembles a full wave rectifier.

    if N=2^m you don't need any multiplier. So, you need N registers, N-1 sub/add circuits ("sub" if x[n-k]<0 and "add" if x[n-k]>=0) and a hardwired arithmetic shifter.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    i would drop the scale factor and build this particular filter with a CIC-like structure. the actual filter becomes 2 adders (well 1 add 1 subtract).

    input => absolute value => CIC