 Prof. Lixi Huang, University of Hong Kong
Personal profile: Lixi was educated at Beijing University of Aeronautics and Astronautics (BUAA) and University of Cambridge. His bachelor and master degrees from BUAA were in the field of aerospace engineering (jet propulsion), while his PhD study at Cambridge was on theoretical acoustics and respiratory biomechanics. He worked as a research associate at the Whittle Lab (of turbomachinery), then as a college research fellow at Peterhouse, both within the University of Cambridge. He taught at HK PolyU from 1996 before joining the University of Hong Kong in 2006 where he is now a professor and deputy head at the department of mechanical engineering. He serves as an associate editor for Journal of Sound and Vibration, Journal of the Acoustical Society of America, and the nature partner journal (npj) Acoustics. He is also an editorial board member for Chinese Journal of Acoustics, and a fellow of the Acoustical Society of America.
Presentation title: Coupling between sound waves and electromagnetic forces
Abstract: We consider an acoustic interface, a diaphragm, which has a moving coil immersed in a magnetic field. When a shunt circuit is added, electrical current flows when incident sound pushes the diaphragm and the coil to cross the magnetic field. The resulting oscillating Lorentz force gives extra acoustic impedance for the interface. This impedance can be easily adjusted by circuit components for passive control purposes. In this talk, we illustrate two useful applications. In the first, the circuit is used to create very high mechanical resistance to achieve sound insulation by light structures. In the second, an electronic switch is installed to allow the circuit to be connected and disconnected at a pre-set time sequence. The frequency spectrum of the incident sound is modified. When part of the low-frequency sound is transformed to high frequency sound, it is easily absorbed by normal means. |