diff --git a/calibrate.py b/calibrate.py
new file mode 100644
index 0000000..d693f9c
--- /dev/null
+++ b/calibrate.py
@@ -0,0 +1,42 @@
+import numpy as np
+import common
+import wave
+import pylab
+
+Tsample = 1
+t = np.arange(int(Tsample * common.Fs)) * common.Ts
+sig = np.exp(2j * np.pi * common.Fc * t)
+sig_dump = common.dumps(sig)
+
+def send():
+    p = wave.play('-', stdin=wave.sp.PIPE)
+    while True:
+        p.stdin.write(sig_dump)
+
+def recv():
+    out = wave.record('-', stdout=wave.sp.PIPE).stdout
+    while True:
+        data = out.read(len(sig_dump))
+        _, x = common.loads(data)
+        x = x - np.mean(x)
+
+        c = np.abs(np.dot(x, sig)) / (np.sqrt(0.5 * len(x)) * common.norm(x))
+        z = np.dot(x, sig.conj()) / (0.5 * len(x))
+        amp = np.abs(z)
+        phase = np.angle(z)
+        peak = np.max(np.abs(x))
+        print('coherence={:.3f} amp={:.3f} phase={:.1f} peak={:.3f}'.format(c, amp, phase * 180 / np.pi, peak))
+
+def plot(x, z):
+    pylab.plot(x)
+    pylab.plot((sig * z).real)
+    pylab.show()
+
+if __name__ == '__main__':
+    import sys
+    opt, = sys.argv[1:]
+    if opt == 'send':
+        send()
+    if opt == 'recv':
+        recv()
+