The measurement of noise can be a rather complicated task. At least, it must not be taken for granted. One problem is that noise is a dynamic phenomenon. The other problem is that a microphone often affects the acoustical field it is trying to sense. These are strange phenomena to those of us who deal only with slowly varying signals and with transducers which do not affect their environment. The object of this paper is to list and explain the precautions that must be taken when measuring noise and documenting acoustical data for SAE criteria.