diff --git a/src/yapsut/colored_noise.py b/src/yapsut/colored_noise.py
index 907c72c5eb2fa85cb50064c5c36dbe4a555c224c..055d7f433793001d2a8c228d75021185e0fd9dab 100644
--- a/src/yapsut/colored_noise.py
+++ b/src/yapsut/colored_noise.py
@@ -92,10 +92,10 @@ Keywords:
       #
       self._freq=np.fft.rfftfreq(self.N)
       #
-      pl=self.alpha/2
+      pl=self.alpha
       with np.errstate(divide='ignore'):
          x=self.fknee/np.where(self._freq==0, np.inf , self._freq)
-         self._S=(1+x)**pl
+         self._S=(1+x**pl)**0.5
       #
       if self._zero_policy=='0' :
          self._S[0]=0.
@@ -104,7 +104,7 @@ Keywords:
       elif self._zero_policy=='M' :
          self._S[0]=self.wn_mean
       elif self._zero_policy=='100x1' :
-         self._S[0]=1 if fknee>ff[1] else (1+100*self.fknee/self._freq[1])**pl 
+         self._S[0]=1 if fknee>ff[1] else (1+100*(self.fknee/self._freq[1])**pl)**0.5
       else : # self._zero_policy=='I' :
          # left things as they are
          pass