Ribeiro, B. and Lenzi, A., "Resonators With Orifices For High-Pressure Tubes of Hydraulic Steering Systems," SAE Technical Paper 2012-36-0130, 2012, doi:10.4271/2012-36-0130.
One of the most important complaints about noise in small vehicles is related to the hydraulic steering pump, which is used strongly during parking maneuvers, and produces a noise that overcomes the one coming from the engine, due to its low speed. This noise can be eliminated by the introduction of two resonators inside the high-pressure tube designed to coincide with the tube's resonance frequency. However, in some cases, as in tubes with short rubber pieces, these resonators may be not sufficient to reduce the noise to non-audible levels, due to its low ability to absorb the pressure peaks coming from the pump. In these cases it is possible to introduce orifices at each resonator to maximize its effect. Here we present the theory related to the use of these orifices and the results obtained in tests on bench.