INPUT TRANSDUCTION ERRORS IN ACTIVE ACOUSTIC ABSORBERS

The sensitivity of an active absorber system to errors in the transduc tion of the acoustic variables used as inputs to the controller is exa mined. Both absorber systems using direct observation of surface press ure and velocity and those deriving control inputs from two spaced pre ssure microphones are considered. It is demonstrated that the total er ror in the transduction of input variables must be smaller than 1 dB i n magnitude and 5 degrees in phase for any system to achieve greater t han 95% absorption coefficient.