Measurements of normal incidence surface impedance using the single transfer function method with multitone periodic random noise signal

Abstract

Commonly used signals for determining the transfer function of a linear filter are pure tone excitation, white noise, or a pseudorandom noise (MLS) signal. However, it is known that the accuracy of this measurement depends strongly on the kind of signal used. In order to try to improve the quality of the measurement, multitone periodic random noise signal properties are investigated in the case of the normal incidence surface impedance measurement. Kundt’s tubes and free-field impedance results using a single microphone transfer function method are given in a large frequency range (20–4000 Hz) for a multitone periodic random noise signal. These results are compared with those obtained with pure tone, white noise, and MLS signal excitation. Also, the influence of noise immunity is investigated for each type of signal.