Material design for hydraulic silencers

Mitigation of fluid-borne noise in hydraulic power systems is of paramount importance for both machine reliability and human comfort. One typical approach involves using compliant inline hydraulic silencers to lower the sound speed within devices, e.g., pressurized bladders or syntactic foams. However, the exploration of innovative compliant materials for silencer designs has been limited; this is largely due to the absence of a comprehensive model that can accommodate a large range of anisotropic materials to evaluate the performance of hydraulic silencers. In this work, we develop a general analytical model for silencer design that incorporates anisotropic reflective materials. The model enables us to identify optimized solutions within a broader material spectrum, tailored to meet pressure-resistance requirements. Building upon these insights, we design and fabricate an anisotropic compliant metallic lattice with low impedance and integrate it into a hydraulic silencer as the reflective material. Experimental results demonstrate that this silencer can achieve an average sound-transmission loss of 21 dB across a frequency range of 100 Hz to 2 kHz, in good agreement with predictions from our proposed model. This work paves the way for selecting and designing innovative materials for the mitigation of hydraulic noise.