ABSTRACT
In accordance with the definition of instantaneous sound intensity as the product of the instantaneous acoustic pressure and the instantaneous particle velocity, an intensity measurement system should, in principle, incorporate transducers of each of these two quantities. However, it transpires that direct transduction of particle velocity is not necessary, and one of the principal current commercial measurement systems implements an indirect transduction principle. It is, of course, imperative that the presence of the transducers distorts (diffracts) the sound field to an acceptably small degree, and that the transducer assembly does not vibrate at audio-frequencies with a velocity amplitude comparable with the particle velocity of the acoustic field (typically 1O-4 m S-I).
