$($a$)$ Assuming that the system has a sampling rate of $8000Hz,$ plot the $IR$ filter frequency responses for the following cases: $=0\mathrm{.}5$ and $R=1$;$=0\mathrm{.}6$ and $R=4$;$=0\mathrm{.}7$ and $R=10,$

and characterize the frequency responses.

$($b$)$ After implementing the multiple$-$echo generator using the following code:

$y=$ filter $([1],[1$zeros$(1,R-1)-$ alpha $],x)$

Evaluate the sound effects of processing the speech file $("$sppech$.$dat"$)$ for the following cases: $=0\mathrm{.}5$ and $R=500(62\mathrm{.}5ms)$;$=0\mathrm{.}7$ and $R=1,000(125ms$

$(250ms),$ and $=0\mathrm{.}5,R=4,000(500ms).$