A study on the leakage error in the spectrum of acoustic intensity

Acoustic intensity is usually estimated from the cross-spectrum of acoustic pressures measured by two adjacent microphones. The cross-spectrum, calculated by the digital Fourier transform technique, has unavoidable leakage error because the signal period does not usually coincide with the record length. Therefore, acoustic intensity, estimated by a conventional FFT analyzer, has distorted values. In our research, the expression of Fourier-transformed data of a harmonic signal with a single frequency was formulated when there was leakage error. A method to eliminate the effect of leakage error from contaminated data was also investigated. Some numerical examples show the validation of the proposed method.