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Altera_Forum
Honored Contributor I
989 Views

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?
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3 Replies
Altera_Forum
Honored Contributor I
38 Views

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
Honored Contributor I
38 Views

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
Altera_Forum
Honored Contributor I
38 Views

Yeah, this sounds better.

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