A sound source includes a tubular resonator configured to be filled with a gas. The exterior of the resonator includes rigid and elastomeric portions. The interior of the resonator includes a first volume and a second volume. The volumes are separated by a rigid tubular wall containing at least one orifice. The at least one orifice enables a flow of gas between the volumes. The resonator also includes at least one rigid tubular member configured to move along the rigid tubular wall. The position of the at least one rigid tubular member regulates at least one dimension of the path between the volumes. The sound source also includes a volume velocity actuator disposed within the resonator. The sound source also includes a processing circuit configured to provide a control signal to cause the volume velocity actuator to perturb the gas within the resonator at a defined frequency.