Master Thesis (m/w/d): Numerical and experimental investigations on a tunable acoustic metamaterial

Fraunhofer LBF, Elektromechanik / 9.7.2019

Electrical / Hybrid Vehicles.
Interior noise tonal components in Electric Vehicles.

The internal noise from electrical vehicles presents significant amount of tonal high frequency components, due to the electrical motors (also called whine noise) and the power electronics. The tonal behavior is highly related to the point of operation for powertrain system, such as speed and rotation.

Those tonal high-frequency components are transmitted into the passenger compartment through the air (airborne noise) and causes annoyances on the passengers. Despite the global noise levels are lower than in Internal Combustion Engines (ICE) vehicles, the tonal noise became more pronounced and, consequently, reduces the pleasantness levels of the car. In order to reduce the tones, the use of passive only solutions may not achieve the required reducing level. Then, active/adaptive acoustic resonators could accomplish a suitable solution. As the tones vary with rotation and/or speed, the resonators must be tuned continuously.

The proposal goal is to develop a panel with embedded periodic resonators (probably Helmholtz resonators) and an active auxiliary system to tune the resonators (in a certain range) to the desired frequency. The experimental noise characterization of a pure electric vehicle is on course.

General overview of the project steps:

  • Knowledge improvement of acoustic metamaterials subject;
  • Finite Element models development, considering sensitivity analysis;
  • Panel design and system specifications based on the numerical results;
  • Prototype construction, most probably considering addictive manufacturing;
  • Experimental investigations will be performed in an electrical vehicle in order to validate the material/system acoustic behavior.


What you bring:

From the student (m/f) is expected commitment, willingness to learn and an independent way of working to achieve practical results. Knowledge in the field of Acoustics, Finite Element Analysis and active systems are welcomed. Experience in ANSYS and common CAD programs are an advantage.

What you can expect:

Supervision by the Research Group System Reliability, Adaptive Structures and Machine Acoustics (SAM) in cooperation with the Fraunhofer Institute for Structural Durability and System Reliability LBF. The necessary work equipment will be provided. The work must be fully documented and should not exceed a period of approx. 6 months.