a1=-15*log10(164*10^(4))+80 
b1=-29*log10(1640000)+167
f1=5:5:1640; f2=1645:5:4000;
for i=1:length(f1)
a(i)=-15*log10(1000*f1(i))+80;
end
for j=1:length(f2)
b(j)=-29*log10(1000*f2(j))+167;
end
n=length(f1)+length(f2);
c(1:1:length(f1))=a; c(length(f1)+1:1:n)=b;
f3=5:5:4000;
plot( f3,c)