If you do not see any changes after filtering it means that all signal components pass through your filter. To visualize it and compare filter response and signal spectrum (use FFT for it) add this string in your script, may bee it can help you.
d = fdesign.lowpass('Fp,Fst,Ap,Ast',f_pass,f_stop,1,60);
Hd = design(d);
values "1, 60" are defaluts for "lowpass" command.