What is the onomatopeia for loud?

There isn't a single, universally recognized onomatopoeia for "loud" itself. However, there are many onomatopoeias that represent *the sounds of loud things*.

Here are some examples:

* BOOM: For explosions, loud crashes, or heavy objects hitting the ground.

* BANG: For loud gunshots, doors slamming, or sudden, forceful impacts.

* CLANG: For the loud ringing of metal on metal, like bells or hammers.

* ROAR: For the loud sound of engines, animals, or powerful voices.

* SCREAM: For loud, piercing cries.

The specific onomatopoeia used depends on the *type* of loud sound you want to represent.