The utility model provides an in-ear earphone, and relates to the technical field of earphones. The in-ear earphone comprises a housing, a
flat panel loudspeaker and an auxiliary diaphragm. The housing has a front end and a rear end. The
flat panel loudspeaker is arranged in the shell and divides an inner cavity of the shell into a front cavity close to the front end and a rear cavity close to the rear end; the auxiliary vibrating diaphragm is arranged in the rear cavity, and the auxiliary vibrating diaphragm and the
flat panel loudspeaker are arranged at intervals. When the in-ear earphone is used, the flat panel loudspeaker pushes air in the rear cavity to move towards the rear end of the shell, so that the auxiliary vibrating diaphragm moves backwards, and the auxiliary vibrating diaphragm becomes a sound load of the flat panel loudspeaker. Due to the existence of the load, the sound order and the
sound quality are greatly improved, so that the bass is enhanced. When the bass dynamic state is large, the air in the rear cavity is not compressed, so that the
radiation area of the flat panel loudspeaker and the
radiation area of the auxiliary diaphragm can be calculated through superposition. According to the sound
radiation principle of the loudspeaker, after the radiation area is increased, the
low frequency can better dive, the linear amplitude is reduced, and the bass is enhanced.