moving things around and adding examples for mic hat code

seeed-voicecard-fork-for-higher-kernel/tools/coherence.py

@@ -0,0 +1,44 @@
+"""
+Estimate the magnitude squared coherence estimate,
+
+- requirements
+    sudo apt install python-numpy python-scipy python-matplotlib
+"""
+
+
+import sys
+import wave
+import numpy as np
+from scipy import signal
+import matplotlib.pyplot as plt
+
+if len(sys.argv) < 2:
+    print('Usage: python {} audio.wav'.format(sys.argv[0]))
+    sys.exit(1)
+
+wav = wave.open(sys.argv[1], 'rb')
+channels = wav.getnchannels()
+frames = wav.readframes(wav.getnframes())
+fs = wav.getframerate()
+wav.close()
+
+print("channels: %d" % channels)
+print("rate    : %d" % fs)
+print("frames  : %d" % wav.getnframes())
+
+array = np.fromstring(frames, dtype='int16')
+
+ch0 = array[0::channels]
+
+fig, ax = plt.subplots()
+
+for ch in range(1, channels):
+    f, c = signal.coherence(ch0, array[ch::channels], fs, nperseg=1024)
+    ax.semilogy(f, c, label="CO 1-%d" % (ch + 1))
+
+legend = ax.legend(loc='lower right', shadow=True, fontsize='small')
+
+plt.xlabel('frequency [Hz]')
+plt.ylabel('Coherence')
+plt.show()
+