Digital Audio Signal Processing, 3rd Edition

Chapter 6Equalizers

U. Zölzer

Spectral sound equalization is one of the most important methods for processing audio signals. Equalizers are found in various forms in the transmission of audio signals from a sound studio to the listener. The more complex filter functions are used in sound studios. However, in almost every consumer product like car radios, hi‐fi amplifiers etc., simple filter functions are used for sound equalization. We first discuss basic filter types followed by the design and implementation of recursive audio filters. In the third and fourth sections, linear‐phase non‐recursive filter structures and their implementation are introduced.

6.1 Basics

For filtering of audio signals, the following filter types are used.

• Lowpass and highpass filters with cutoff frequency (3 dB cutoff frequency) are shown with their magnitude response in Fig. 6.1. They have a passband in the lower and higher frequency range, respectively.
• Bandpass and bandstop filters (magnitude responses in Fig. 6.1) have a center frequency and a lower and upper and cutoff frequency. They have a ...