Frequency Devices, Inc. offers this valuable design guide about analog and digital filters. Many basic principles taught in a signal processing class are discussed, such as sampling a signal, aliasing, and frequency-domain analysis. The equations and parameters that govern filter operation are well explained. The guide defines many of the considerations necessary to choose which type of filter...

A professor in Stanford University's Center for Computer Research in Music and Acoustics is the author of this online book on digital filters. The material is mainly geared toward musicians, but it can be useful for anyone learning about digital signal processing. Available in draft form as of March 2003, the book contains equations, theorems, and principles of filter design spread across many...