# High Frequency NVH

High frequency NVH is an implementation of Statistical Energy Analysis (SEA), and is used to predict and analyze the vibration and acoustic response of complex dynamic systems. It is a method of analyzing the flow of energy between dynamic systems based on a statistical coupling between the response modes of the systems. The high frequency NVH is a pre- and post-processor; the solver used for the analysis is SEAM.

The Statistical aspect of SEA refers to its approach to the description of systems and their dynamic parameters. SEA treats the resonance frequencies and mode shapes of a structure or acoustic space as random variables. As a result, the SEA predictions are also statistically described in terms of the mean and standard deviation of the response variable.

The Energy aspect of SEA refers to the dynamic energy used to describe the state of a vibrating system. The flow of dynamic energy through the system is determined and related to dynamic response variables such as acceleration or sound pressure.

The Analysis aspect of SEA is that it preserves parameter dependence so that the effects of design modifications can be studied.

The SEA model of vibrational energy transmission is similar to a diffusion model of thermal energy transmission. Just as thermal energy flow (conduction) is proportional to temperature differences between connected elements, vibrational energy flow is proportional to modal energy differences between connected subsystems.

The structure and acoustic spaces to be modeled in high frequency NVH are broken down into elements. Elements are parts of the system that can be identified as simple geometric entities. Each element is modeled by one or more subsystems, each representing a group of resonant modes that share similar characteristics. The elements are connected to each other at high frequency NVH connections, which model the degrees-of-freedom at the boundaries between elements.

A wide variety of model input loads can be specified. Some of the power that is injected into the system is dissipated in damping and the remainder is transmitted to other subsystems. The solution of the SEA model is found by solving a set of power balance equations to obtain the subsystem modal energies. Subsystem acceleration or sound pressure levels are then calculated from the modal energies. Calculated power flows between subsystems aid in the ranking of energy transmission paths.

High frequency NVH imports third-party XML files with acoustic connections and structural-acoustic connections, converted into SEAM subsystems for solving.