a substrate sidewall comprising a first surface and a second surface that are set opposite to each other;

a cavity surrounded by the substrate sidewall;

a ring bracket accommodated in the cavity;

a sounding assembly locating on the first surface of the substrate sidewall and sealing an opening of the cavity on the first surface, comprising a first sounding assembly locating between the substrate sidewall and the ring bracket, and a second sounding assembly inside the ring bracket;

wherein

the first sounding assembly includes a plurality of first driving parts each having a first fixed end fixed to the ring bracket, and a first free end connected to the first fixed end and extending in a direction close to the substrate sidewall;

a first gap is formed between the first free end and the substrate sidewall;

a second gap is formed between the first free ends of two adjacent first driving parts;

the first sounding assembly further includes a first flexible diaphragm connecting the substrate sidewall and the first free end and sealing the first gap, a second flexible diaphragm connecting the first free ends of the two adjacent first driving parts and sealing the second gap;

the second sounding assembly includes a plurality of second driving parts each having a second fixed end fixed to the ring bracket, and a second free end connected to the second fixed end extending away from the substrate sidewall;

a third gap is formed between the second free ends of two adjacent second driving parts;

the second sounding assembly further includes a third flexible diaphragm connecting second free ends of two adjacent second driving parts and sealing the third gap,

the first flexible diaphragm has an arch shape arching away from the first gap, the second flexible diaphragm has an arch shape arching away from the second gap, the third flexible diaphragm has an arch shape arching away from the third gap.