Designing silent electric machines: uncertainties & optimization


In all industrial sectors, electric machines emit noise of electromagnetic origin with high-pitched tonal components that are very unpleasant to the ear.

  • In the railway sector, traction motors are the source of exterior and interior noise.
  • In the automotive sector, if the traction motors reduce external noise, this is not the case for the internal noise where these sounds become annoying. In a context of increasing power density, this problem will become more acute in the years to come.
  • Accessories for the hybridization of thermal engines and electric actuators present in vehicles are also concerned, the acceptance criterion being to not hear them.
  • In addition to high noise levels, a strong dispersion of the noise levels – exceeding 5 dB – is observed on samples leaving production. This dispersion is detrimental to the quality image of the product.


The technical objectives of the e-Silence project are twofold:

To develop multiphysics numerical methods for the silent and robust design of rotating machines. The innovations of the project are as follows:

  • To take acoustics into account from the beginning of the machine design cycle to quickly estimate the impact of the electromagnetic design on radiated noise.
  • To develop multi-harmonic optimization methods for the shapes of the active parts of the machine in order to reduce electromagnetic excitations “at the source”.
  • To understand the physical phenomena at the origin of noise dispersion by means of tests on a batch of machines taken from the factory. Integrate methods to take into account the uncertainties in the simulations.
  • To develop techniques for the reduction of electromagnetic and dynamic structural models in order to reduce calculation time.

These methods will be used to develop low-noise machine concepts. Two electrical machines, designed by MMT for automotive applications, will be used as support. The work consists in optimizing machine topology to reduce electromagnetic excitations and vibroacoustic response, and in demonstrating the interest of endowing the resin coating with an “acoustic” function, by optimizing resin to reduce noise.

The project will build a base of expertise with methodologies, software and services on the vibration of all types of electrical machines. This will support the French industry in mastering these aspects in a more electric world.


Union Européenne




This project was selected in the framework of the call for projects FUI-AAP23 of the Single Inter-Ministerial Fund (FUI). It is subsidized by the Public Investment Bank (BPI France) and the AURA region via the European Regional Development Fund (ERDF – this project is co-financed by the European Union).