A whistle is provided with an interior that can be cleaned. The whistle has a body with a resonance chamber wall. One face of a resonance chamber formed by the resonance chamber wall is open. A side plate is formed separately from the body, and can be attached to and removed from the body. The side plate has a first portion that blocks the one face of the resonance chamber when attached to the body. A first flange is provided on the first portion and is engageable with the resonance chamber wall. At least one of the resonance chamber wall and the first flange is elastically deformable. An air passageway, the resonance chamber, an air opening that is opened in the air passageway, and a sound-emitting opening that is opened in the resonance chamber are formed by the body and the side plate.