The near field acoustic holography technique for cyclostationary sound field and its experimental research

One Near field Acoustic Holography (NAH) technique is proposed for analyzing cyclostationary sound field. The signal of this kind of sound field has very serious modulation phenomenon generally, in spectrum of which obvious sidebands exist. It is difficult for the traditional NAH to possess demodulation function, so virtual power of sidebands exists in its hologram. Replacing the Fourier's transform with the second-order cyclic statistics, the proposed NAH technique uses the Cyclic Spectral Density (CSD) function as reconstructed physical quantity, instead of the spectrum or power spectral density of pressure signal. The CSD function can demodulate cyclostationary signals, which makes no virtual power of sidebands in its hologram. The results of simulation and experiment show that the proposed NAH can extract more information about cyclostationary sound field than traditional NAH, by which sound field can be known more clearly.