**6. Conclusions**

The study presents the acoustic simulation and experiment of radiated noise in a multi-stage pump. The following results were obtained:

(1) The sound pressure level in the multi-stage pump increases first and decreases afterward with the increment of the flowrate. The sound pressure level reaches its lowest value at 0.8*Q*d, which corresponds to maximum efficiency working conditions. The sound pressure level of the radiated noise in the multistage pump rises linearly with the increase of the rotational speed.


**Author Contributions:** Q.S. and C.W. conceived and designed the experiments; G.L. performed the experiments and simulation; B.W. and K.H. analyzed the data; Q.S. wrote the paper; J.Y. funding acquisition.

**Funding:** This research was funded by National Key R&D Program of China (2018YFC0810505), National Natural Science Foundation of China (51976079, 51779107), Senior Talent Foundation of Jiangsu University (15JDG048), Open Foundation of National Research Center of Pumps, Jiangsu University (NRCP201604).

**Conflicts of Interest:** The authors declare no conflict of interest.
