Acoustical simulation and evaluation of load-dependent hydraulic engine mounts using two-port description

Hydraulic engine mounts, consisting of an elastomeric part and an additional hydraulic damping mechanism, became generally accepted in the automotive industry within the last decades. For a target sound design of the interior noise of a passenger car, the transfer paths from the engine via the engine mounts into the passenger compartment play an important role. To influence these vibroacoustic paths, the transfer behavior of an engine mount needs to be designed in detail in frequency range and preferably as a function of the load state of the engine. In this paper, several purposeful acoustic lay-out designs of hydraulic engine mounts with load-dependent transmission characteristic are presented. The complex acoustical transfer function of a hydraulic mount has been linearized for several operating points and implemented in a one-dimensional analytical calculation model using 2-port descriptions. The parameters of the model were measured on the components of a modular engine mount. The calculation tool has been used to evaluate different concepts of mounts with load-dependent transmission characteristics. Parameter studies showed high potential of three different concepts which have been build up as prototypes and verified on a test rig.