"Luckily there are many sites that now provide audio files under a creative commons licence. You can use these freely, as long as you attribute the original source. Sometimes you can even licence them to use commercially if you wish."
In a world where anyone with an internet connection can access, create and share information, opinions and beliefs, it has become increasingly important that students are not only able to assess the credibility of sources but also to look more deeply at the underlying motivations, beliefs and bias of the creator.