An explosion-proof system for generating acoustic energy. An exemplary embodiment of the system includes a main housing defining an open housing space and an opening. A cover structure is configured for removable attachment to the main housing structure to cover the opening and provide an explosion-proof housing structure. The cover structure includes an integral head mass. An acoustic energy emitting assembly includes the head mass, and an excitation assembly disposed within the explosion-proof housing structure. An electronic circuit is disposed within the explosion-proof housing structure to generate a drive signal for driving the excitation assembly to cause the acoustic energy emitting assembly to resonate and generate acoustic energy. In one embodiment the acoustic energy is a beam of ultrasonic energy useful for testing ultrasonic gas detectors. A method is also described for testing ultrasonic gas leak detectors using an ultrasonic source.