ABSTRACT
This chapter introduces acoustic instrumentation and discusses condenser, electret and piezo-electric microphones. It examines sound intensity analysers and particle velocity sensors and explores instrumentation for sound source localisation. The most commonly used sound pressure transducer for precision measurement is the condenser microphone. A condenser microphone consists of a diaphragm that serves as one electrode of a condenser, and a polarised backing plate, parallel to the diaphragm and separated from it by a very narrow air gap, which serves as the other electrode. Condenser microphones in particular are sensitive to both humidity and dust on the diaphragm, both of which cause a high level of self-noise in the instrument. The recording of noise for subsequent analysis is sometimes very convenient, especially when undertaking fieldwork. The identification of the actual location of sources of sound on vibrating structures or surfaces in air flows is of great interest to any noise control engineer.
