A pole-zero placement technique for designing second-order IIR parametric equalizer filters

Toon van Waterschoot, Marc Moonen

Still RelevantIntermediate

A new procedure is presented for designing second-order parametric equalizer filters. In contrast to the traditional approach, in which the design is based on a bilinear transform of an analog filter, the presented procedure allows for designing the filter directly in the digital domain. A rather intuitive technique known as pole-zero placement, is treated here in a quantitative way. It is shown that by making some meaningful approximations, a set of relatively simple design equations can be obtained. Design examples of both notch and resonance filters are included to illustrate the performance of the proposed method, and to compare with state-of-the-art solutions.

Summary

This paper presents a direct digital-domain procedure for designing second-order IIR parametric equalizer filters using a quantitative pole-zero placement technique. The authors derive simple approximate design equations and demonstrate the method with notch and resonance filter examples, comparing results to bilinear-transform-based designs.

Key Takeaways

Design second-order IIR (biquad) parametric equalizers directly in the digital domain using pole-zero placement.
Compute pole and zero locations and convert them to filter coefficients with the paper's closed-form approximations.
Evaluate and tune notch and resonance filter responses by adjusting pole radius and angle to control bandwidth and depth.
Compare the direct-digital approach with bilinear-transform analog designs to understand accuracy, complexity, and implementation trade-offs.

Who Should Read This

Intermediate DSP engineers or graduate students working on audio, speech, or communications filter design who want a practical, low-complexity method to implement second-order parametric equalizers.

Still RelevantIntermediate

Topics

Filter Design Audio Processing FFT/Spectral Analysis