sonitus

Sonitus, sonitus, m., fourth declension, from sono, sonare, sonui, "to sound". As with every fourth declension noun the nominative singular, genitive singular and nominative plural are all sonitus, so the article a translator supplies is guesswork until the rest of the clause arrives. The ablative singular sonitu is the form the corpus favours, usually as an ablative of cause or means: at the sound of, because of the noise of.

Beside it sits sonus, soni, second declension, covering the same ground more neutrally. The distinction is not watertight, but sonitus leans loud: the crash, the din, the roar of water or weapons, where sonus will do for a note or a tone. Sonus is what a lyre makes; sonitus is what a collapsing building makes.