Clown Trumpet (5e Trap)
From D&D Wiki
A clown trumpet is usually attached to a wall or floor and magically geared to activate whenever it senses motion within 100 feet of it. Whe triggered, the clown trumpet emits a blaring noise and all creatures within 100 feet of it that can hear it must succeed on a DC 15 Constitution saving throw or take 6d6 thunder damage. A creature that fails the save by 3 or less is also stunned until the end of its next turn. After the clown trumpet is triggered, it can't be triggered again until a creature resets it with 1 minute of work and a successful DC 15 Intelligence (Arcana) check. TOOT!