Acoustic emission signals carry potentially useful information about the criticality of deformation source mechanisms in materials, but signal processing techniques such as threshold counting, RMS voltage recording, peak detection, and spectral analysis often failed to extract such information unambiguously. The difficulty lies in the determination of the transfer characteristics of the structure and the sensor. We report experimental results of a computer‐based test system consisting of a large plate and a capacitive transducer [N. N. Hsu, J. A. Simmons, and S. C. Hardy, Materials Evaluations35(10), 100–106 (1977)]. The transient wave propagation behavior of the plate and the transfer function of the capacitive transducer are known. Consequently, unknown sources can be characterized by solving the Töplitz matrix directly. Explicit force‐time functions of simulated signals such as breaking glass capillaries, breaking pencil leads, dropping steel balls, electrical arcs, and pulsed piezoelectric transducers have been determined. These force‐time functions are then used to determine experimentally the transfer characteristics (impulse‐response) of various propagation structures and various ultrasonic transducers.