Abstract: A pneumatic sweep generator for use as an audio source in tests near vocal frequency ranges. A horn, whose volume may be controlled by air pressure and whose tone may be controlled by air velocity, is connected to an air supply in a dual-circuit arrangement. Mechanical control devices, such as manual and pressure release valves, are located within the circuit to provide for tone and volume control. A reciprocating air cylinder continuously varies the air velocity within the horn to sweep the frequencies in an adjustable manner. Electromagnetic interference is totally eliminated by a complete absence of electrical devices in either the device or in necessary controls.