Numerical simulation and experimental investigation were performed on flow-induced exterior noise characteristics of a centrifugal pump as turbine (PAT). Under typical flow conditions, the dipole sources were obtained using Reynolds-average method. The flow-borne noise and flow-induced structure noise due to impeller and casing source in exterior acoustic field were solved by FEM/AML. On the basis of this, the spectrum characteristics of each noise source and their contribution to exterior noise were distinguished. Meanwhile, the free modal parameters for casing were recognized by modal experiment. Results show that the average relative error of natural frequency between calculation and experiment is less than 4.60% under approximate mode of vibration. The sound pressure at five order blade passing frequency (BPF) becomes the highest due to the influence of casing structure, and the second order BPF comes second. The flow-induced structure noise due to casing source is the biggest contributor to exterior noise, followed by flow-borne noise due to casing source, and the flow-borne noise due to impeller source is least. The results can provide some reference for low noise design of similar turbomachinery.