In this work we proposed a bi-stable acoustic energy harvester (BAEH) to scavenge noise energy. The nonlinear BAEH is composed of a piezoelectric cantilever beam with a flat plate attaching at the free end, a curved plate, a movable magnet and a fixed magnet. The incident and reflecting sound waves will produce dynamic acting forces on the front and the back of the flat plate, thereby exciting the plate to oscillate and take snap-through between equilibrium positions, and thus give a large output. The experimental results prove that the BAEH can execute snap-through at a relatively low intensity of noise. It can reach coherence resonance and thus generate a large output voltage. It is found that the separation distance d is a key factor for occurrence of snap-through. Therefore, for a given sound pressure level (SPL), the BAEH can be optimized to reach coherence resonance and generates the maximum output power. (C) 2017 Elsevier Ltd. All rights reserved.