Flat drywall ceilings are typically 8–10 ft. A flat hard ceiling over a hard floor is the classic recipe for a fast, ringing flutter echo.
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.