

In [1]:

    
import numpy, scipy, matplotlib.pyplot as plt, urllib, IPython.display
plt.rcParams['figure.figsize'] = (14,5)

Zero Crossing Rate

The zero crossing rate indicates the number of times that a signal crosses the horizontal axis.

Let's load a signal:



In [2]:

    
x, fs = librosa.load('simple_loop.wav')

Listen to the signal:



In [3]:

    
IPython.display.Audio(x, rate=fs)









    Out[3]:

Plot the signal:



In [4]:

    
librosa.display.waveplot(x, sr=fs)









    Out[4]:





<matplotlib.collections.PolyCollection at 0x1078b0050>

Let's zoom in:



In [5]:

    
plt.plot(x[1500:2000])









    Out[5]:





[<matplotlib.lines.Line2D at 0x1078eb390>]

I count three zero crossings. Let's compute the zero crossings using librosa.



In [6]:

    
zero_crossings = librosa.zero_crossings(x[1500:2000], pad=False)

That computed each individual zero crossing. To find the total number of zero crossings, use sum:



In [7]:

    
print sum(zero_crossings)

To find the zero-crossing rate over time, use zero_crossing_rate:



In [8]:

    
zcrs = librosa.feature.zero_crossing_rate(x)
print zcrs.shape

Plot the zero-crossing rate:



In [9]:

    
plt.plot(zcrs[0])









    Out[9]:





[<matplotlib.lines.Line2D at 0x1079a0210>]