[Objective] This study aims to address the issue of electromagnetic vibration and noise caused by complex air-gap electromagnetic force waves in dual-rotor synchronous motor (DRSM) with fractional-slot concentrated windings and low pole-slot numbers. [Methods] The 6-slot stator and 2/4-pole DRSM were selected as the research object to analyze the characteristics and modulation mechanism of electromagnetic force waves under no-load and load conditions. The magnetomotive force and air-gap flux density analytical expressions were derived based on the magnetic potential-permeance method

while the force wave characteristics were theoretically analyzed using Maxwell’s stress tensor method. The finite element model was validated through no-load back-electromotive force experiments

and the time-space spectrum of force waves as well as armature reaction effects were investigated through simulations. For the yoke-less stator design

a tooth shoe structure was developed

and its vibration and noise suppression effectiveness was evaluated via multiphysics field simulations. [Results] The spatial orders of the electromagnetic force waves were found to be multiples of the greatest common divisor of the pole number and slot number

while the temporal frequencies were even multiples of the fundamental frequency. The load current was observed to only alter the amplitude of the force waves without changing their order characteristics. The tooth shoe structure was demonstrated to reduce the amplitude of the first-order magnetic permeability-modulated force waves by 31.01%

with significant attenuation observed in the 4th-order vibration acceleration and high-frequency noise. [Conclusion] The tooth shoe structure effectively suppresses specific-order electromagnetic force waves by modulating the magnetic permeability distribution

providing both theoretical foundations and engineering solutions for vibration and noise reduction in DRSM.