f=200:200:3400;

for i=1:18


h=sin(pi*f./8000)./(pi*f./8000);
g=20.*log10(h);
end
plot(f,g)
d=0.25
    eta=10^(-d/10)

figure
z=[0 100 200 500 599 1000 1800 100000];
F=(z+600)./(z-600);
F1=abs(F);
ad=6+20.*log10(F1)

z1=[0 100 200 500 599 1000 1800 100000];
a=4;b=exp(2*a/8.68);
G=F1.*b;
zin=ones(size(z1));
for i=1:length(z1);
if z1(i) <= 600;


zin(i)=600*(G(i)-1)/(G(i)+1);
	else
zin(i)=600*(G(i)+1)/(G(i)-1);
	end
end
plot(z1,zin)