Investigating the Acoustical Properties of Bubbly Liquids. The speed of sound waves varies as the mediums through which they travel vary. The speed of sound waves traveling through water is approximately 1500 m/s while the speed of sound in air is approximately 340 m/s. One might expect that a combination of the two, that is, air and water, would result in the speed of sound through the medium being somewhere between the speed of sound in air and the speed of sound in water. However, this is not the case. The presence of the air bubbles in the water changes the compressibility of the fluid. As a result of this change, the speed of sound waves through the fluid is affected. The resulting effects on the speed of sound are mainly dependent on three variables. These are the frequency of the sound being transmitted, the size of the bubbles in the mixture, and the concentration of the bubbles, or void fraction, in the mixture. The theory of Commander and Prosperetti 1 describes the speed of sound waves at different frequencies and void fractions, however there has been great difficulty in obtaining data to support this theory in the area around bubble resonance and also the area in which sound travels at supersonic speeds. In 1994, Cheyne et al 2 conducted research using a fiber optic laser interferometer and a standing wave method. They were able to make measurements of the phase speed in the area where sound travels at supersonic speeds, but later had problems reproducing their results. The experiments conducted and described in this paper serve the purpose of testing the standing wave method, in order to reproduce the past results obtained by Cheyne et al. New methods were also employed which used the detection of the loading on the sound source to obtain data near or at the single bubble resonance.