rat-tat-tat

Onomatopoeic.

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.

rat-tat-tat (plural rat-tat-tats)

1. Such a sound.
   • 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:

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

   • 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:

     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.

• The tat syllable may be repeated further to convey a sound of longer duration.