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+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test IIRFilterNode GetFrequencyResponse</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="webaudio.js"></script>
+  <script type="text/javascript" src="biquad-filters.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(function() {
+  // Modified from WebKit/LayoutTests/webaudio/iirfilter-getFrequencyResponse.html
+  var sampleRate = 48000;
+  var testDurationSec = 0.01;
+
+  // Compute a set of linearly spaced frequencies.
+  function createFrequencies(nFrequencies, sampleRate)
+  {
+    var frequencies = new Float32Array(nFrequencies);
+    var nyquist = sampleRate / 2;
+    var freqDelta = nyquist / nFrequencies;
+
+    for (var k = 0; k < nFrequencies; ++k) {
+        frequencies[k] = k * freqDelta;
+    }
+
+    return frequencies;
+  }
+
+  // Number of frequency samples to take.
+  var numberOfFrequencies = 1000;
+
+  var context = new OfflineAudioContext(1, testDurationSec * sampleRate, sampleRate);
+
+  var frequencies = createFrequencies(numberOfFrequencies, context.sampleRate);
+
+  // 1-Pole IIR Filter
+  var iir = context.createIIRFilter([1], [1, -0.9]);
+
+  var iirMag = new Float32Array(numberOfFrequencies);
+  var iirPhase = new Float32Array(numberOfFrequencies);
+  var trueMag = new Float32Array(numberOfFrequencies);
+  var truePhase = new Float32Array(numberOfFrequencies);
+
+  // The IIR filter is
+  //   H(z) = 1/(1 - 0.9*z^(-1)).
+  //
+  // The frequency response is
+  //   H(exp(j*w)) = 1/(1 - 0.9*exp(-j*w)).
+  //
+  // Thus, the magnitude is
+  //   |H(exp(j*w))| = 1/sqrt(1.81-1.8*cos(w)).
+  //
+  // The phase is
+  //   arg(H(exp(j*w)) = atan(0.9*sin(w)/(.9*cos(w)-1))
+
+  var frequencyScale = Math.PI / (sampleRate / 2);
+
+  for (var k = 0; k < frequencies.length; ++k) {
+    var omega = frequencyScale * frequencies[k];
+    trueMag[k] = 1/Math.sqrt(1.81-1.8*Math.cos(omega));
+    truePhase[k] = Math.atan(0.9 * Math.sin(omega) / (0.9 * Math.cos(omega) - 1));
+  }
+
+  iir.getFrequencyResponse(frequencies, iirMag, iirPhase);
+  compareChannels(iirMag, trueMag);
+  compareChannels(iirPhase, truePhase);
+
+  // Compare IIR and Biquad Filter
+  // Create an IIR filter equivalent to the biquad filter. Compute the frequency response for both and verify that they are the same.
+  var biquad = context.createBiquadFilter();
+  var coef = createFilter(biquad.type,
+                          biquad.frequency.value / (context.sampleRate / 2),
+                          biquad.Q.value,
+                          biquad.gain.value);
+
+  var iir = context.createIIRFilter([coef.b0, coef.b1, coef.b2], [1, coef.a1, coef.a2]);
+
+  var biquadMag = new Float32Array(numberOfFrequencies);
+  var biquadPhase = new Float32Array(numberOfFrequencies);
+  var iirMag = new Float32Array(numberOfFrequencies);
+  var iirPhase = new Float32Array(numberOfFrequencies);
+
+  biquad.getFrequencyResponse(frequencies, biquadMag, biquadPhase);
+  iir.getFrequencyResponse(frequencies, iirMag, iirPhase);
+  compareChannels(iirMag, biquadMag);
+  compareChannels(iirPhase, biquadPhase);
+
+  SimpleTest.finish();
+});
+</script>
+</pre>
+</body>
+</html>