Not sure how much they sound like guns, but there&#x27;s a whole field of scaring off birds from farms, see e.g. <a href="http:&#x2F;&#x2F;www.birdcontrolpro.com&#x2F;propane_cannons.htm" rel="nofollow">http:&#x2F;&#x2F;www.birdcontrolpro.com&#x2F;propane_cannons.htm</a>