An investigation of Laser Doppler Anemometry (L.D.A.) for the measurement of acoustic velocity fields using the photon correlation method of signal analysis has been made. It is shown how estimates of velocity amplitudes can be obtained for the cases of single tone and band limited noise fields. Measurements made in a travelling wave tube are presented and are shown to compare well with microphone measurements. A discussion is also made of the measurement of complex impedances and possible industrial uses of the technique are mentioned.