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Action potentials are pulses that propagate along the membrane of excitable cells and play a crucial functional role in the behavior of many living organisms. These pulses are typically described as a purely electrical change in transmembrane potential difference, and the mathematical description of action potentials is based on the view that the excitable membrane can be fully represented by an equivalent circuit. However, this approach has come under criticism since many experimental facts are neither readily explained nor predicted by the electrical theory, and there is no derivation of the model equations from basic principles. An alternative view suggests that in action potentials it is acoustic pulses that propagate along the lipid interface and cause a reversible phase transition. The mechanism provided to induce a phase transition in the lipid membrane is similar to propagating phase boundaries seen in fluids and solids. Experimental observations and a theoretical acoustic model demonstrate the following similar properties between action potentials and nonlinear sound waves that propagate within lipid membranes near phase transition: (1) correspondence of time, velocity, and voltage scales, (2) qualitative pulse shape, (3) sigmoidal response to stimulation amplitude (an ‘all-or-none’ behavior), (4) electric and nonelectric manifestations, (5) pulses with similar shapes that arise upon using different types of stimulations, and (6) annihilation upon collision. Falsifiable predictions are made, suggesting that crucial computational information may be overlooked by focusing only on electrical measurements.