Note on the relationship of sound pressure and sound intensity

Abstract It is usual to calculate the sound pressure at a given location by energy addition of all relevant components. Another approach considers the sound power per unit area. This note shows that the two approaches lead to different results for ideal line or planar sources. The calculated sound pressure level is higher than expected on the basis of sound intensity. For this reason, the use of sound pressure levels measured close to a source leads to a sound power estimate which is too high.