rat-tat-tat

1. The sound made by knocking on a door with a hard object (such as a door knocker).
2. The sound made by firing an automatic machine gun.

plural rat-tat-tats

1. Such a sound.

   Then it grew louder and more distinct - it was a clear rat-tat-tat.

   1925 July – 1926 May, A[rthur] Conan Doyle, “(please specify the chapter number)”, in The Land of Mist (eBook no. 0601351h.html), Australia: Project Gutenberg Australia, published April 2019

   1 more example

   To the steady rat-tat-tat of machine guns and exploding bursts of smoke, amphibious tanks slice across a lake not far from the big green mountains that stand along the world’s most heavily armed border.

   2023 November 30, Foster Klug, “South Koreans want their own nukes. That could roil one of the world’s most dangerous regions”, in Associated Press