Auralization of Electrical Machines - the IEM makes Virtual Prototypes "Hearable"Copyright: IEM
As an important part in the analysis and optimization process of the acoustic behavior of electrical machines, the IEM makes use of a technique called "auralization". This means that the emitted noise is synthesized and made hearable to the developer.
This is achieved by the simulation of transfer functions that directly link electromagnetic force waves to the sound pressure at arbitrary listener positions. These transfer functions are solely dependent on the structure of the machine and thus do not depend on the electric or magnetic circuit or on the operating conditions. Consequently, various designs and operating conditions can be auralized and thus be psycho-acoustically evaluated and optimized within a short period and with reasonable effort. The result, i.e. the noise, can directly be perceived. This allows for a more descriptive and more clear evaluation than it could be achieved by means of other methods based, e.g., on the radiated sound power or spectral components.
Moreover, by employing methods of the Virtual Reality, it is possible to synthesize the radiated noise under consideration of environmental influences. A 3D representation of a virtual scenario further improves the impression.
In order to determine the transfer function in an efficient way, various simulation methods are used. Typically, a structural model is generated and a modal analysis is performed by means of the FEM. The free-field sound radiation can either be calculated with an analytical radiation model, which is applicable to cylindrical geometries, or by means of the Boundary Element Method. To simulate the resulting sound pressure, the transfer functions subsequently have to be multiplied by the electromagnetic forces acting at the inner stator teeth. The electromagnetic field simulation can either be performed by using the IEM in-house FEM solver iMOOSE or by analytic methods based on conformal mappings.
Within the field of auralization and acoustic measurements, the IEM cooperates closely with the Institute of Technical Acoustic (ITA) at the RWTH Aachen University.