@Override
    public void update(float tpf) {
        synchronized (threadLock) {
            updateInRenderThread(tpf);
        }
    }
Stops the AL source on the channel, detaches buffers and filters,
and clears the jME source association. Does NOT free the channel index itself.

@param index The channel index to clear.
jme3-core/src/main/java/com/jme3/audio/openal/ALAudioRenderer.java