Acoustic techniques have been developed as multifunctional tools for various microscale manipulations. In prevalent design paradigms, a position-fixed piezoelectric transducer (PZT) is utilized to generate ultrasound waves. However, the immobility of the PZT restricts the modulation of the acoustic field's position and orientation, consequently diminishing the adaptability and effectiveness of subsequent acoustic micromanipulation tasks. Here, we proposed a miniaturized soft acoustic end-effector and demonstrated acoustic field modulation and microparticle manipulation by adjusting PZT position and orientation. The PZT is mounted on the end of a soft robotic arm that has three individual degrees of freedom and can be deformed in 3D space by inflating or deflating each chamber. Experiments showed that the soft acoustic end-effector can change the traveling direction of microparticles and modulate the location of a standing wave field. Our approach is simple, flexible, and controllable. We envision that the soft acoustic end-effector will facilitate multiscale acoustic manipulation in interdisciplinary applications, especially, for in vivo acoustic therapies.