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New voice energy efficiency measures voice are defined from the integral mechanical energy equations for laryngeal flow and for the vocal tract.  These equations are used to identify energy utilization mechanisms in terms of their role as energy input, output, storage, or loss.  Two new efficiencies are defined:  the laryngeal acoustic efficiency, and the vocal tract acoustic efficiency.  The former characterizes the effectiveness of the sound source, and the latter of transmission of sound.  These efficiencies are estimated from a reduced-order modeling of phonation, measurements in a physical model of the human upper airway, and high-fidelity aeroelastic-aeroacoustic simulation.