Acoustic impedance measurement using sine sweep excitation and known volume velocity technique

The direct determination of acoustic impedance requires the measurements of both pressure and volume velocity, but the latter in general cannot be measured directly. Thus, other means must be adopted to bypass this measurement problem. This paper presents two methods which utilize excitation of a system with known volume velocity. This, along with measured pressure response, provides both magnitude and phase of impedance as continuous functions of frequency. The first method uses a convertible acoustic horn driver for excitation. Its volume velocity is determined by measuring calibrated pressure in a fixed cavity at the back of the driver. The second method uses for excitation an electrodynamic shaker driven piston which carriers an accelerometer. This signal is integrated to yield input acoustic velocity information. The two‐channel analog signal processing setup includes the following instruments: sine sweep oscillator, tracking filters, log converters, phase meter, etc. In order to establish the validi...