title: sine wave that exponentialy changes between frequencies f1 and f2 at given time/amount of samples
body: <p>I'm trying to implement Python method that generates sine wave, which ramps up between two freq exponentially.
  Linear change was solved in <a href="https://stackoverflow.com/questions/11199509/sine-wave-that-slowly-ramps-up-frequency-from-f1-to-f2-for-a-given-time">[this question]</a> with following Python code:</p>
  
  <pre><code>from math import pi, sin
  
  def sweep(f_start, f_end, interval, n_steps):    
      for i in range(n_steps):
          delta = i / float(n_steps)
          t = interval * delta
          phase = 2 * pi * t * (f_start + (f_end - f_start) * delta / 2)
          print t, phase * 180 / pi, 3 * sin(phase)
  
  sweep(1, 10, 5, 1000)
  </code></pre>
  
  <p>How to change this linear accumulative phase/delta approach to expotential frequency sweep and be smooth to human ear.</p>