adding echo in matlab

hi there I would like to add an echo to a downloaded sound track using FIR and IIR filters this is the code I wrote so far

[soundfile,frqs]=wavread('C:\Users\Downloads\Blackberry_Ringtone_35.wav');

K = 200; % filter order
g = -0.1; % decay rate (was changed to different values)
b_K = -g;
a_K = 1;
b = [1 zeros(1,K-1) b_K]; 
a = [1  zeros(1,K-1) a_K];
y =filter(b,a,soundfile);
wavplay(y,frqs)

however the code is not working since it doesn't add any effect to the sound track

Answer 1

[Walter Roberson]

Remember that sounds information is read in with each channel being a column. Your filter appears to be trying to go across rows.

[A A]

thank you for your fast reply..can you elaborate more...do u mean I should transform the givens into columns??