Hybrid Active Noise Control Structures: A Short Overview

The classical feedforward and feedback active noise control structures can be combined in pairs into hybrid control systems, in order to partially compensate for their individual limitations. The increase in complexity is compensated by the flexibility and attenuation performance they can achieve together. Several combination strategies can be found in the literature in different application contexts and formulated using different nomenclatures. This paper provides a single source for the existing hybrid control structures in a purely digital implementation. For each one of them a block diagram in context of active noise control headphones is provided. To describe the interaction between the classical structures within the hybrid system, changes in the transfer functions and effective plants are discussed.