<a href="https://en.wikipedia.org/wiki/Air_horn" class="extiw" title="w:Air horn">Air horn</a> powered by pressurized air in can, from Italy.  When the valve on the top is pressed, air from the can flows past a reed in the throat of the horn, causing it to vibrate, generating a loud note.  Gas air horns like this are used as foghorns in small boats, and bicycle horns.
<a href="//commons.wikimedia.org/wiki/User:Edvvc" title="User:Edvvc">Edvvc</a>
<span class="int-own-work" lang="en">Own work</span>