4 SecTion | 1 Test and Measurement the principles of operating one analyzer can usually be applied to another after a short indoctrination period. Measurement sys- tems are like rental cars: you know what features are there, you just need to find them. In this chapter I will attempt to provide a sufficient overview of the various approaches to allow the reader to investigate and select a tool to meet his or her measurement needs and budget. The acoustical field testing of sound rein- forcement systems mainly involves measurements of the sound pressure fluctuations produced by one or more loudspeakers at various locations in the space. Microphone positions are selected based on the information that is needed. This could be the on- axis position of a loudspeaker for system alignment purposes, or a listener seat for measuring the clarity or intelligibility of the system. Measurements must be made to properly calibrate the system, which can include loudspeaker crossover settings, equal- ization, and the setting of signal delays. Acoustic waveforms are