The inventive audible warning device includes, in a preferred embodiment, a refillable pressurized air tank having a service port, a cover for covering the service port, an air pump integrated with the tank for filling the tank within pressurized air, an activator for regulating air flow, a hose connecting the tank to the activator, and a horn connected to the activator. The cover also includes a relief valve for depressurizing the tank. In addition, the cover includes locking elements for locking the cover, which can include in turn a rotatable handle that triggers the relief valve when the locking elements are unlocked. A method for producing sound is also disclosed herein.