Abstract: A method for testing a loudspeaker includes receiving a response signal characterizing a response of the loudspeaker to a stimulus signal, the response signal including a number of parts, each part including a reproduction of a corresponding part of the stimulus signal and distortion, computing a distortion spectrum including a plurality of distortion values. The computing includes, for each part of the response signal, processing the part of the response signal to determine a first value characterizing a human perceptible component of the distortion present in the part of the response signal, processing the part of the response signal to determine a second value characterizing a degree of harmonic distortion of the part of the response signal, and forming a distortion value for the part of the response signal based on a combination of the first value and the second value. A test result is formed based on a comparison of the distortion spectrum to a threshold.

Abstract: A circuit for conditioning an acoustic transducer driving signal includes an inner feedback circuit having a test signal input for receiving a test signal, a feedback input for receiving a feedback signal, circuitry for forming an output signal including circuitry for amplifying the input signal according to the feedback signal, and an output for providing the output signal. The circuit also includes an outer feedback circuit having a signal input for receiving the output signal from the inner feedback circuit, a desired offset input for receiving a signal representative of a desired output offset, a first low-pass filter circuit for detecting an actual offset in the output signal, signal combination circuitry for forming the feedback signal including combining the actual offset with the desired output offset, and a feedback output for providing the feedback signal to the feedback input of the inner feedback circuit.

Abstract: A circuit for conditioning an acoustic transducer driving signal includes an inner feedback circuit having a test signal input for receiving a test signal, a feedback input for receiving a feedback signal, circuitry for forming an output signal including circuitry for amplifying the input signal according to the feedback signal, and an output for providing the output signal. The circuit also includes an outer feedback circuit having a signal input for receiving the output signal from the inner feedback circuit, a desired offset input for receiving a signal representative of a desired output offset, a first low-pass filter circuit for detecting an actual offset in the output signal, signal combination circuitry for forming the feedback signal including combining the actual offset with the desired output offset, and a feedback output for providing the feedback signal to the feedback input of the inner feedback circuit.