Active control of free-field sound using near-field energy-based error signals

Abstract

Practical efforts to actively control sound often require error sensors located in the acoustic or geometric near field of primary and secondary sources. Unfortunately, when using conventional acoustic pressure sensors, control performance often becomes very sensitive to sensor position, and optimal sensor positions are difficult to ascertain or maintain with changing system conditions. Other types of error sensors or combinations of error sensors may produce fewer position-dependent complications, yielding excellent global sound-field control with greater ease and consistency. This paper compares the use of potential, kinetic, and total energy density error signals in the near field of a primary and secondary source in free space. It also discusses the distinct spatial and spectral uniformities of these quantities and their impact on the active control of sound.