Leave is a signifier to represent fresh, young and energetic. And glass is like an invisible coverage.
Leave is being moved by the motor, and turned around in the bottle. They are struggling and trying to break the glass. Every bottle is in different shape and color, which would be represented different difficulties of living. The leaves are fighting against the glasses and the sound will come out. They are resonance with each other. The motor sound is like a water of river. The hitting sound is like answering the water of river.