PhD Defence by Birgitte Bække

Abstract

Balanced armature receivers are powerful and power-efficient, high-fidelity, miniature loudspeakers. The combination of these traits makes it the only receiver transducer technology used in hearing aids. When the receiver produces sound, the vibrations of the internal components propagate to the receiver chassis, which then propagate to the hearing aid structure. These vibrations are picked up by the hearing aid microphones nearby and reproduced, thus creating a feedback loop.

To understand and predict the vibration pattern of the receiver, a simple, computationally light model is developed. The model predicts the movement of the receiver chassis, based on an analysis of the motion of the internal components. The model is generally applicable to different types of receivers and the model parameters can be adjusted to reflect the specific receiver type. These devices have a built-in asymmetry, which means the chassis both translates and rotates. The model is validated against measurements and a more complicated numerical model. Comparison demonstrated good agreement between the models.

Supervisors

• Principal supervisor: Associate Professor Vicente Cutanda Henriquez, Department of Electrical and Photonics Engineering, DTU
• Co-supervisor: Professor MSO Frieder Lucklum, Department of Electrical and Photonics Engineering, DTU

Evaluation Board

• Associate Professor Cheol-Ho Jeong, Department of Electrical and Photonics Engineering, DTU
• Dominique Rodrigues, Head of the Acoustic & Vibration department, Laboratoire national de métrologie et d'essais (LNE), France
• Peter Møller Juhl, Siemens-Gamesa, Brande, Denmark

Master of the Ceremony

• Associate professor Jonas Brunskog, Department of Electrical and Photonics Engineering, DTU