Balanced MEMS loudspeaker: Coulomb forces vs. viscosity of air and squeeze film damping
Miniaturized micro-electro-mechanical systems (MEMS) loudspeakers is a current developmental trend for in-ear audio applications. However, when a loudspeaker shrinks to a size of a microelectronic chip, the involved physics starts to differ from the macroscopic world. At one side, an electrostatic MEMS loudspeaker benefits from small electrode gaps leading to high driving forces. At the same time, the fluid dynamics of the air can cause strong damping forces inside the microscopic cavities of a µSpeaker chip. In our presentation, we discuss the influence of the fluid dynamics on the damping of a balanced nanoscopic electrostatic drive (NED) test loudspeaker design. We analyze simulation results and link them to experimental observations done with a high-speed camera. Understanding the various sources of fluid dynamic damping is of high importance for the design of high fidelity MEMS audio transducers.