Source Code for Module gmisclib.bark_scale

 1  from gmisclib import Num 
 2   
 3  """Perceptual frequency scales.""" 
 4  __version__ = "$Revision: 1.3 $" 
 5   
 6  if hasattr(Num, 'asinh'): 
 7          asinh = Num.asinh 
 8  else: 
 9 -        def asinh(x): 
10                  tmp = Num.greater(x, 0) 
11                  p = Num.log(x + Num.sqrt(x*x + 1)) 
12                  n = -Num.log(-x + Num.sqrt(x*x + 1)) 
13                  return tmp*p + (1-tmp)*n 
14   
15 -def acosh(x): 
16          assert not Num.greater(x, 1) 
17          return Num.log(x - Num.sqrt(x*x-1)) 
18   
19 -def f_to_bark(f): 
20          """frequency to critical band number. 
21          See Schroeder et al. (1979). 
22          """ 
23          return 7*asinh(Num.asarray(f)/650.0) 
24   
25 -def bark_to_f(b): 
26          """critical band number -> frequency 
27          M. R. Schroeder, B.S. Atal, J.L. Hall (1979), J.Acous.Soc.Am. 66(6) 1647-1652. 
28          Title: "Optimizing Digital Speech Coders by exploiting masking 
29          properties of the Human Ear." 
30          """ 
31          return 650*Num.sinh(Num.asarray(b)/7.0) 
32   
33   
34 -def cbw(b): 
35          """Critical bandwidth (in Hz) at frequency b (barks).""" 
36          return (650.0/7.0)*Num.cosh(b/7.0) 
37   
38   
39  if __name__ == "__main__": 
40          print f_to_bark(51) 
41          print f_to_bark(149) 
42