Metal roof deck are often 14–30 ft. Common in gyms, warehouses and big-box stores; rain noise on the deck can also be a problem.
At 500 Hz the bare ceiling absorbs about 5% of the sound that reaches it. In a room with a hard floor, the ceiling and floor reflect sound back and forth, so treating the ceiling is often the single most effective step.
Options: clouds, baffles or ceiling tiles.