A spiral conveyor with automatic flow control includes a plurality of curved segments connected to form a spiral for the flow by gravity of articles from an upper level to a lower level. The cross-sectional area of the at least one passage aperture in the interposer is to be designed as significantly smaller than the lateral extension of the diaphragm structure of the MEMS component. The sound radiated from the back surface of the electro-acoustic transducing unit is attenuated on being transmitted into the inside of the sound duct to prevent the radiated sound from being re-admitted into the electro-acoustic transducer.