**6. Conclusions**

To investigate the isolation effectiveness of flexible pipes, a scaled model test was carried out. Four types of pipe, i.e., SLMB, DLMB, BCR and RP, were considered. Tests were carried out under 1700 r/min, 2000 r/min, 2300 r/min and 2600 r/min. By calculation the transfer coefficient, the isolation effectiveness was established. The test results under four different conditions showed some consistency as well as some inconsistencies. Nevertheless, DLMB, BCR and RP showed their own advantages in different frequency under all conditions. The primary features are as follows:


**Author Contributions:** Contributed to Synthesis, Testing, Data Analysis, and Writing the Manuscript: Y.Y. (Yang Yang); Suggested and Supervised the Work: G.P. and S.Y.; Contributed to Revising the Language of the Manuscript: Y.Y. (Ying Yuan). All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Natural Science Basic Research plan in Shaanxi Province of China grant number [2019JQ-071].

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