I'm quite new to javascript but I think you're question is the same as what I was trying to do and now I have found the answer. Instead of calling the recorder.exportWAV function you call the recorder.getBuffer(getBufferCallback) function as you can see below. I hope this helps. it works for me.
function stopRecording() {
recorder.stop();
recorder.getBuffer(getBufferCallback);
//recorder.exportWAV(function(s) {
//source = window.URL.createObjectURL(s);
//audio.src = source;
//});
}
function getBufferCallback(buffers) {
window.newSource = context.createBufferSource();
window.buffers0 = buffers[0]; /*store the buffers in a variable so you can use them in future*/
window.buffers1 = buffers[1];
var newBuffer = context.createBuffer(2, window.buffers0.length, context.sampleRate);
newBuffer.getChannelData(0).set(window.buffers0);
newBuffer.getChannelData(1).set(window.buffers1);
window.newSource.buffer = newBuffer;
window.newSource.connect(context.destination);
window.newSource.start(0);
}