diff --git a/content/media/webaudio/test/test_mediaDecoding.html b/content/media/webaudio/test/test_mediaDecoding.html
index f8b62ed9e41..4a19213158f 100644
--- a/content/media/webaudio/test/test_mediaDecoding.html
+++ b/content/media/webaudio/test/test_mediaDecoding.html
@@ -107,8 +107,6 @@ function createWaveFileData(audioBuffer) {
 
 SimpleTest.waitForExplicitFinish();
 
-var cx = new AudioContext();
-
 // fuzzTolerance and fuzzToleranceMobile are used to determine fuzziness
 // thresholds.  They're needed to make sure that we can deal with neglibible
 // differences in the binary buffer caused as a result of resampling the
@@ -191,9 +189,9 @@ var files = [
   //  // A wave file
   //  //{ url: "24bit-44khz.wav", valid: true, expectedUrl: "24bit-44khz-expected.wav" },
   // A non-audio file
-  { url: "invalid.txt", valid: false },
+  { url: "invalid.txt", valid: false, sampleRate: 44100 },
   // A webm file with no audio
-  { url: "noaudio.webm", valid: false },
+  { url: "noaudio.webm", valid: false, sampleRate: 48000 },
   // A video ogg file with audio
   {
     url: "audio.ogv",
@@ -237,9 +235,9 @@ function checkAudioBuffer(buffer, test) {
   if (Math.abs(buffer.duration - test.duration) >= 1e-3) {
     ok(false, "got: " + buffer.duration  + ", expected: " + test.duration);
   }
-  is(buffer.sampleRate, cx.sampleRate, "Correct sample rate");
+  is(buffer.sampleRate, test.sampleRate, "Correct sample rate");
   // Take into account the resampling when checking the size
-  var expectedLength = test.frames * cx.sampleRate / test.sampleRate;
+  var expectedLength = test.frames * buffer.sampleRate / test.sampleRate;
   ok(Math.abs(buffer.length - expectedLength) < 1.0, "Correct length", "got " + buffer.length + ", expected about " + expectedLength);
 
   var wave = createWaveFileData(buffer);
@@ -248,6 +246,7 @@ function checkAudioBuffer(buffer, test) {
 
 function runTest(test, response, callback) {
   var expectCallback = false;
+  var cx = new OfflineAudioContext(1, 1, test.sampleRate);
   cx.decodeAudioData(response, function onSuccess(asyncResult) {
     ok(expectCallback, "Success callback should fire asynchronously");
     ok(test.valid, "Did expect success for test " + test.url);
@@ -293,29 +292,27 @@ function loadNextTest() {
 function callbackShouldNeverRun() {
   ok(false, "callback should not fire");
 }
-expectTypeError(function() {
-  cx.decodeAudioData(null, callbackShouldNeverRun, callbackShouldNeverRun);
-});
-expectTypeError(function() {
-  cx.decodeAudioData(undefined, callbackShouldNeverRun, callbackShouldNeverRun);
-});
-expectTypeError(function() {
-  cx.decodeAudioData(123, callbackShouldNeverRun, callbackShouldNeverRun);
-});
-expectTypeError(function() {
-  cx.decodeAudioData("buffer", callbackShouldNeverRun, callbackShouldNeverRun);
-});
-expectTypeError(function() {
-  cx.decodeAudioData(new Uint8Array(100), callbackShouldNeverRun, callbackShouldNeverRun);
-});
+(function() {
+  var cx = new AudioContext();
+  expectTypeError(function() {
+    cx.decodeAudioData(null, callbackShouldNeverRun, callbackShouldNeverRun);
+  });
+  expectTypeError(function() {
+    cx.decodeAudioData(undefined, callbackShouldNeverRun, callbackShouldNeverRun);
+  });
+  expectTypeError(function() {
+    cx.decodeAudioData(123, callbackShouldNeverRun, callbackShouldNeverRun);
+  });
+  expectTypeError(function() {
+    cx.decodeAudioData("buffer", callbackShouldNeverRun, callbackShouldNeverRun);
+  });
+  expectTypeError(function() {
+    cx.decodeAudioData(new Uint8Array(100), callbackShouldNeverRun, callbackShouldNeverRun);
+  });
+})();
 
-if (cx.sampleRate >= 44100) {
-  // Now, let's get real!
-  loadNextTest();
-} else {
-  todo(false, "Decoded data tests disabled; context sampleRate " + cx.sampleRate + " not supported");
-  SimpleTest.finish();
-}
+// Now, let's get real!
+loadNextTest();
 
 </script>
 </pre>