Experimental verification of an Electromagnetic Shunt Damping circuit parameters producing an anechoic surface inside an acoustic tube

The Electromagnetic Shunt Damping as a method of semi-active sound damping is introduced. An electrodynamic loudspeaker is utilized as an anechoic surface inside an acoustic tube when connected to convenient shunting circuit. The theoretical values of an ideal shunt circuit are simulated based on expected parameters of experimental setup with an acoustic tube. Segments of complex impedance progression are selected based on a feasibility study of theoretical results. The shunt circuits with given values of complex impedance are implemented using RL and RC circuits and negative impedance converter. The theoretical values of complex shunting impedance are experimentally verified in the overall frequency range from 50 to 300 Hz. The experimental results in relevant frequency bands show good overall correspondence with theoretical values with a significant shift in frequency which raises new questions and challenges for future development.