Abstract: A pneumatic engine for metering or controlling of flow of compressed gas. is disclosed. In certain embodiments, the flow may be used to sound a whistle. The engine may include a body comprising a first chamber having an exit aperture, a second chamber having an entrance aperture, and a bolt aperture connecting the first chamber to the second chamber. A bolt may be positioned within the bolt aperture and extending into the first chamber and into the second chamber. The bolt may comprise a conduit extending therewithin. The conduit may place the first chamber in fluid communication with the second chamber. The bolt may selectively travel within the body through a range of motion. The range of motion may comprise a first position wherein the bolt blocks the exit aperture and a second position wherein the bolt does not block the exit aperture.