Shunted loudspeakers for transformer noise absorption

Transformer noise is mainly composed by the fundamental frequency component around 100 Hz and its harmonics. Sometimes it is difficult to apply traditional sound absorption treatments especially at the fundamental frequency and its second harmonic due to space constraints. Instead of radiating sound, loudspeakers can also be considered as an effective resonant absorber and its absorption performance can be adjusted by employing a shunt circuit at its terminals. This paper introduces a novel loudspeaker absorber with a shunt circuit, which is optimized based on the nonlinear model of the loudspeaker for the transformer noise absorption. Resistances, capacitances and inductances are used to adjust the electrical parameters of the loudspeaker in order to change its acoustic impedance. The proposed absorber shows excellent low frequency absorption performance at the transformer noise frequencies, but is much thinner than the traditional sound absorbers. Numerical simulations and the experiments are carried out to verify its feasibility.