Active noise control - Systems and Applications Design

This article deals with applications of active noise control, which reduces noise by opposing it with "counter-noise" of the same amplitude but opposite sign, emitted by secondary sources. The concept dates back to the 1930s, but the few attempts to implement and exploit it were largely unsuccessful. In the 1970s, the physical basis for this type of control was established by the seminal work of Maurice Jessel (see [BR 3 010] ). In the 1980s, advances in digital signal processing made it possible to create adaptive systems capable of generating the signals required for proper operation at any time and without any external action. This progress led to the birth of the first industrial applications of active control and, from the 2000s onwards, to the marketing of numerous products. This article first describes the signals needed to implement active control (signals specific to active control, signals for data acquisition, processing and restitution, and signals for communication with a host computer). It then describes system architecture (sensors, input and output modules, controllers, actuators and drive) and the choice of components (filters, analog-to-digital converters, digital-to-analog converters) and processors (specific integrated circuits, programmable gate circuits, microcontrollers, general-purpose microprocessors or signal processing processors). It then looks at the applications of active control and the main industrial applications resulting from it (ear muffs, silencers, the automotive industry, the aeronautics industry and home protection). The final section is devoted to the psychoacoustic aspects of this control and its use in improving sound quality in automotive, rail and air transport.