kani

This is my program

x=wavread('E:\project\kani imp\akk');
l=size(x)

l =

78336 2

>> s=1;
>> for t=[4000:4000:l]
sum=0;
for t1=[s:t]
sum=sum+(sum(abs(x.^2)));
en=sum;
enm=en+1;
end
end
I have this error ??? Subscript indices must either be real positive integers or logicals
how can i fix this this problem