[Objective] To address the issue of electromagnetic vibration and noise in spoke-type permanent magnet synchronous motor (STPMSM), this study investigates the impact of additional air gap between the stator teeth and yoke on the acoustic performance of STPMSM. The aim is to reduce electromagnetic vibration and noise by designing an optimal additional air-gap structure. [Methods] Firstly, a finite element model of the STPMSM was developed to analyze its electromagnetic field characteristics. The electromagnetic force was decomposed into radial and tangential components using the Maxwell stress tensor method and two-dimensional Fourier transform to examine its spatiotemporal distribution. Then, a 10-pole 12-slot STPMSM test platform was constructed to simulate vibration and noise responses under actual operating conditions. Modal analysis, hammer response experiments, and frequency response function measurements were conducted to validate the simulation results. Finally, a comparative study was performed between uniform and non-uniform additional air gap structures, evaluating the effects of triangular and convex tooth-yoke separation structures on overall acoustic performance. [Results] Both simulation and experimental results demonstrated that introducing an additional air gap between the stator teeth and yoke reduced the motor's sound pressure level by approximately 2.3 dB. Finite element analysis revealed that the dominant radial force components corresponded to specific spatial harmonics, aligning with actual noise frequencies. Although the non-uniform additional air gap introduced new spatiotemporal components of electromagnetic force, its impact on overall acoustic performance was negligible. Furthermore, the stator with a triangular tooth-yoke separation structure exhibited significantly better noise reduction performance than the convex structure. [Conclusion] This study confirms that the additional air gap effectively reduces electromagnetic vibration and noise in STPMSM. The difference in acoustic performance between uniform and non-uniform air gaps was not significant, while the triangular tooth-yoke separation structure demonstrated superior noise reduction capabilities. Furthermore, optimizing additional air gap parameters using genetic algorithms can further enhance acoustic performance, offering new insights and methodologies for motor noise control.