Digital Acoustic Intensity Techniques in Gasoline Engine Noise Studies

This paper describes the use of digital measurements to assess acoustic intensity close to the various surfaces of a two litre gasoline engine. Using phase-locked data acquisition an acoustic power balance is constructed for the engine which is shown to correlate well with three other methods - lead covering, average surface vibration level and close microphone. However, the prediction of sound pressure level from these power balances is shown to be difficult, at least at 1 m from the surface. A simple relationship between acoustic intensity and sound pressure level in the frequency domain has been found.