The Simple Feedback Comb Filter

What happens when we multiply the output of a delay line by a gain factor then feed it back to the input?

**Figure 19:** The signal flow diagram of a comb filter.
$\begin{figure}\centerline{\scalebox{1}{% \input{comb2.pstex_t}}}\end{figure}$

The difference equation for this filter is

$\displaystyle y(n) = x(n) + gy(n-M),$

If the input to the filter is an impulse

$\displaystyle x(n)=\{1,0,0,\ldots\}$

the output (impulse response) will be ...

**Figure 20:** Impulse response for filter .
$\begin{figure}\centerline{\scalebox{.8}{% \input{comb2imp.pstex_t}}}\end{figure}$

``Mus 270a: Introduction to Digital Filters'' by Tamara Smyth, Department of Music, University of California, San Diego.