The cyclostationary characteristics can not be extracted clearly in reconstruction of the acoustic field radiated from the cyclostationary sources by the conventional near-field acoustic holographyp rocedures. The cyclostationary near-field acoustic holographym ethod uses the cyclic spectrum density function as the reconstruction variance instead of the spectrum or the power spectrum density,which decomposes the carrier wave and modulating wave in the appropriate cyclic frequency. The reconstructed CSD shows the distribution of the modulating wave of cyclostationary sources and supplies more cyclostationary acoustical information than the conventional NAH. In the present work, the theory of the cyclostationary NAHcombined with the wave superposition is introduced, which can be used for the arbitrarily shaped cyclostationary sources. Anumerical simulation and aspeaker experiment are employed to validate this WSA-based cyclostationay NAHmethod. The results of the simulation showg reat agreement between the reconstruction and the analytical value. The distribution of the CSD of the cyclostationary acoustical source on the surface coincides with the speaker box accurately.

This paper focus on parameter estimation of periodic frequency modulated (PFM) signals, which can be observed from periodic phenomena in nature. For example, radar returns scattered from a walking person. In this work, a method for estimating the period of the PFM signal is proposed, which combines time-frequency distribution (TFD) and cyclic spectrum density (CSD). TFD is used to transform the nonstationary PFM signal into a stationary one with the same period while CSD can estimate the period of a signal in low signal to noise (SNR) ratio case. The properties of TFD and CSD enable the proposed algorithm to extract period of the PFM signal with various modulation forms, and moreover, with a high precision in the low SNR case. Experiments with both synthetic data and measured data confirm the effectiveness of the proposed method.