A single transducer that is part of a positive or negative feedback circuit can achieve active acoustic absorption and reflection. It is shown that the mobility of the diaphragm is dependent on the load of the voice coil. By using the four-pole mathematics, we show a direct relationship between the electrical and acoustical terminals of the transducer. The test setup as well as the results by the subtraction of impulse responses are discussed. Even the sound transmission through the diaphragm is a part of this investigation. Possible applications will be discussed.
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