Musical Ferrite

Unwanted tones can, for example, appear in voltage transformers. Vibrations of components made out of ferrite cause noise and lead to damage in machines. This phenomenon triggered the research question:

To what extent can the vibrations of a ferrite rod inserted into a periodically changing magnetic field be described by physical theory?

This paper gives a theoretical explanation of the phenomenon involving magnetism and acoustics. Vibrations of the ferrite rod were justified by the theory of magnetostriction. Various experiments were conducted to create the expected sound triggered by the vibrations of the ferrite rods. Measuring the sound waves was an appropriate way to test the phenomenon as the rod's vibrations cause air pressure waves and thus audible sounds. The predicted frequencies of the sound waves were experimentally confirmed, the frequency spectrum was generated with a Fast Fourier Transform. The relationships between the intensity of a ferrite rod's vibrations (amplitude of the sound) and the rod's material (analyzed: ferrite's magnetic permeability, coercive magnetic field strength) or dimensions (analyzed: rod's length and volume) were experimentally tested, but could only be partially explained.

This paper also includes an experience report of the Swiss Young Physicists' Tournament, where the phenomenon will be debated in 2020.