A comparison of ANR headset performance for loopshaping and H∞ control system design

Abstract

Active noise reduction (ANR) has been widely accepted as a critical component in circumaural hearing protectors and communication headsets for many commercial and military applications. That is because ANR headsets provide the end-user with at-ear noise suppression that is more effective than passive configurations alone can offer. In the past few years, there have been significant advances in this technology area. These are largely related to attempts to transition from traditional analog control hardware to digital implementations. One benefit of digital controller design is the ease of constructing optimal and robust compensators. The traditional approach in designing feedback ANR headsets is usually ‘‘loopshaping,’’ which is a somewhat heuristic design method. The desire for further improvements in feedback ANR headset performance is leading engineers toward more analytical approaches for controller design, including the robust techniques of H∞. This presentation compares and contrasts loopshaping and optimal controller design for the single-input, single-output disturbance rejection problem. A controls engineer experienced in loopshaping design techniques and a controls engineer experienced in optimal controller design techniques compare results for an ANR headset design. Constraints are placed on bandwidth, actuator force, and system design. It is shown that the loopshaping design can perform as good as or better than the optimal control solution for the given constraints.