# Python script for "Duelund 4th 3 ways"

import math
import cmath

fc=716                        # centre frequency
a=3.13                        # factor "a" (damping)
offset=85                     # targets dB offset

inf=15.625                    # start frequency
sup=32000                     # end frequency
N=264                         # number of points (24 * 11 octaves = 264)

file_low=open("low_Duelund.frd","w")       # names of files
file_mid=open("mid_Duelund.frd","w")
file_high=open("high_Duelund.frd","w")

for i in range(0,N+1):
    
    f=inf*(sup/inf)**(i/N)         # frequency sweep
    s=1j*f/fc
    
    low=1/(1+a*s+s**2)**2          # transfer functions
    mid=(2-a**2)*low*s**2
    high=low*s**4
    
    file_low.write(str(f))
    file_low.write("\t")
    file_low.write(str(20*math.log10(abs(low))+offset))
    file_low.write("\t")
    file_low.write(str(cmath.phase(low)*180/math.pi))
    file_low.write("\n")

    file_mid.write(str(f))
    file_mid.write("\t")
    file_mid.write(str(20*math.log10(abs(mid))+offset))
    file_mid.write("\t")
    file_mid.write(str(cmath.phase(mid)*180/math.pi))
    file_mid.write("\n")

    file_high.write(str(f))
    file_high.write("\t")
    file_high.write(str(20*math.log10(abs(high))+offset))
    file_high.write("\t")
    file_high.write(str(cmath.phase(high)*180/math.pi))
    file_high.write("\n")
    
file_low.close()
file_mid.close()
file_high.close()