Determination of radiated sound power by acoustic intensity measurement using Fourier analysis

Tapio Lahti

Research output: Book/ReportReport


A review is given on the theory, applications, measurement techniques and estimation errors of the direct determination of acoustic intensity. Problems encountered with the calibration of equipment and the recording of intensity signals in the field are discussed. A practical system for measuring intensity is described which consists of two microphones, a tape recorder and a dual channel FFT analyzer. The system was calibrated using a new method involving electrostatic actuators. Correct operation of the system was verified in two test measurements, inside a standing wave tube and in a reverberation room. An extension to the two-microphone cross-spectral method of determining intensity is suggested to yield directly the specific acoustic impedance by the aid of two pressure microphones and the FFT processing of the two signals. Further, the impedance can be utilized in the direct determination of the radiation and absorption coefficients.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages74
ISBN (Print)951-38-1480-7
Publication statusPublished - 1982
MoE publication typeD4 Published development or research report or study

Publication series

SeriesValtion teknillinen tutkimuskeskus. Tutkimuksia - Research Reports


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