On the uncertainty in measurement of sound power using sound intensity

An overview is given of the sources of error in intensity-based sound power measurements with the “two microphone” measurement principle, and their effect on the resulting measurement uncertainty is discussed. Comments on existing standards for such measurements and measurement systems are also given. The most important sources of error are phase mismatch, inadequate spatial sampling, electrical noise in the microphones, flow noise due to mean airflow, and unstable background noise. The influence of these factors depends significantly on the sound field conditions.