Technology enthusiast Mike Cook has written an excellent guide describing the theory, basics and operation of pulse-width modulation with regards to an Arduino board. As we don't have any onboard digital to analogue converters, PWM is often used as a reasonable substitute - especially when creating simple tones and sound effects with piezo buzzers.
Towards the end of the tutorial Mike also explains how to increase the ability by explaining the theory of analogue filters and how to design your own. Very useful indeed - so to get started, click here. And we're on twitter and Google+, so follow us for news and product updates as well.