Learn Turkish: Tavandan bir gümbürtü geliyor. - A loud bang is coming from the ceiling.

It is an onomatopoeic word based on the sound güm (a deep, echoing bang or thump). Turkish creates many noun forms for noises by adding suffixes like -tı or -tü to root sounds. You have likely seen this pattern before in words like gürültü (noise) or tıkırtı (clicking/rattling).

Why do we use the verb gelmek (to come) here instead of a verb for "happening" or "being heard"?

In Turkish, sensory inputs like sounds and smells are treated as objects that travel to you. Just as you say koku geliyor (a smell is coming / it smells), you say ses geliyor or gümbürtü geliyor rather than saying "a sound is happening."

How would I apply this lesson's grammar to guess that "A loud bang must be coming from the ceiling"?

You would combine the present continuous form with the auxiliary olmalı. The verb geliyor becomes geliyor olmalı, making the full sentence Tavandan bir gümbürtü geliyor olmalı. This expresses your strong deduction about an ongoing event.

Could we say tavanda (at/on the ceiling) instead of tavandan (from the ceiling)?