Bubbly liquids have long held our attention as a novel medium for acoustic propagation, with nonlinear, dispersive, and attenuative properties that eclipse those present in either the gas or fluid phase alone. For example, when driven at frequencies that are well below the bubble resonance frequency, the material exhibits both high compressibility and high density. This unusual combination results in a mixture sound speed that can range as low as 100 m/s, far less than that of either the air or the water alone. This remarkable effect will be demonstrated by bubbling air through a vertical water-filled tube. The air injection process results in a broadband noise that drives the tube in its fundamental length mode. The frequency of this mode is audible, and scales with the mixture sound speed. By varying the flow rate of air (i.e., the void fraction), it is possible to vary the sound speed and thus control the pitch associated with the tube resonance. Knowledge of this resonance frequency and the length of the tube allows us to determine the mixture sound speed, which can then be compared with theory. [Work supported by ONR.]