We've recently bought a Philips 32PW9618 and am very pleased with it. However, we are yet to hear even a whisper from the rear speakers. When we run the test function there is a hiss from them in turn, the same as the other speakers but we have not heard anything from them in normal viewing. The green transmission light is on. Please could anyone suggest what we could watch or play to confirm whether they are working, or what we may not have done? Sorry if this is a really stupid question!