Design and Characterization of MEMS Optical Microphone for Aeroacoustic Measurement

Abstract

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Design Approaches of MEMS Microphones for Enhanced Performance

“…Figure 19: Shock analysis of a capacitive microphone of up to 80000g acceleration, in which (a) the whole membrane is missing and (b) most of the membrane is cracked [192]. Figure 20: Optical fiber intensity modulated microphones with (a) incident and reflected lights in a single-bundle fiber [196] and (b) incident and reflected lights separated by integrated waveguides [197]. 16 Journal of Sensors the noise issue in the two combined omnidirectional microphones [207].…”

“…The intensity modulation-based microphone can be divided into two configurations: one is where a fiber optic lever is configured in which an incident light source on the membrane is arranged in such a way that, when the membrane moves due to the sound waves, the light reflects back to the photodetector, where it is converted into an electrical signal and processed through an electronic circuitry [195]. This type of microphone is presented in [196], in which the incident and reflected lights are in the same fiber bundle placed near the cavity of the microphone, as shown in Figure 20(a). Another way is to place an integrated waveguide near the cavity to separate the paths of incident light and reflected lights, as shown in Figure 20(b) [197].…”

Bulk micro-machined wide-band aero-acoustic microphone and its application to acoustic ranging

“…Moreover, the small dimensions of such microphones potentially enable the realization of a dense microphone-array and provide a metrology sensor for studying turbulent flows with high spatial resolution. Different sensing mechanisms, such as capacitive [21], piezoelectric [22], optical [23] and piezoresistive [24] have been applied to realize high-frequency aero-acoustic micro-fabricated microphones. Each has its own relative merits and demerits.…”

“…Although piezoelectric transducers can be designed to work in the range of several hundreds of kilohertz, they often operate within a narrow frequency band (due to their resonant behavior) and the sensitivity is relatively low. Optical microphones [23] offer a better immunity to electromagnetic interference and their sensitivity is normally higher than that of the microphones based on other sensing mechanisms. However, the assembly process of aligning an optical fiber to a sensing diaphragm is complicated and limits further dimensional scaling of such microphones.…”