Source Code for Module gmisclib.erb_scale

 1   
 2  """ERB Perceptual frequency scale.""" 
 3   
 4  import math 
 5  import Num 
 6   
 7  __version__ = "$Revision: 1.6 $" 
 8   
 9 -def f_to_erb(f): 
10          """Frequency to ERB band number. 
11          http://ccrma-www.stanford.edu/~jos/bbt/Equivalent_Rectangular_Bandwidth.html 
12          """ 
13          return Num.log(0.00437*f+1)*(21.4/math.log(10.0)) 
14   
15 -def erb_to_f(e): 
16          """ERB number -> frequency 
17          """ 
18          return (10.0**(e/21.4)-1)/0.00437 
19   
20   
21 -def ebw(e): 
22          """Critical bandwidth (in Hz) at frequency e (erbs).""" 
23          return 0.108*erb_to_f(e) + 24.7 
24   
25   
26  if __name__ == "__main__": 
27          print f_to_erb(51) 
28          print f_to_erb(149) 
29