Recent Trends in Structures and Interfaces of MEMS Transducers for Audio Applications: A Review

Abstract

In recent years, Micro-Electro-Mechanical Systems (MEMS) technology has had an impressive impact in the field of acoustic transducers, allowing the development of smart, low-cost, and compact audio systems that are employed in a wide variety of highly topical applications (consumer devices, medical equipment, automotive systems, and many more). This review, besides analyzing the main integrated sound transduction principles typically exploited, surveys the current State-of-the-Art scenario, presenting the recent performance advances and trends of MEMS microphones and speakers. In addition, the interface Integrated Circuits (ICs) needed to properly read the sensed signals or, on the other hand, to drive the actuation structures are addressed with the aim of offering a complete overview of the currently adopted solutions.

MEMS audio speakers *

“…Electrostatic speakers also need a DC offset for stabilizing the diaphragm position, improving linearity, increasing sensitivity, and preventing charge accumulation. The vibrating structure of the speaker can be fed with an input electrical signal in either analog or digital form, but the output needs to be in analog form to be audible to humans [4]. The input electrical circuit primarily consists of a power amplifier and a digital signal processing unit.…”

“…The gain is less linear compared to other types of amplifiers. On the other hand, the use of class-AB type amplifiers is useful to achieve low THD and higher fidelity by compromising on overall efficiency [4]. Efficiency and linearity are well balanced in class AB amplifiers, making them a popular choice as a compromise between class A and class B amplifiers.…”

“…The air pulses propagate outwards the sound outlet in the speaker enclosure. The technical specifications 4 for one of their commercial products summarized from their official website [114] are listed as follows.…”

Linear enhancement of mechanical compliance by zeolite filling in a compact loudspeaker

“…With the surging commercialization of artificial intelligence, compact loudspeakers in pads, cell phones and laptops have become crucial electroacoustic devices for audible communication with high precision and efficiency [1]. When a common loudspeaker shrinks to the millimeter scale, materials [7][8][9][10], with sufficient gas-solid interfaces [11] and large volumes of tortuous channels [12,13], can interact with acoustic waves and thus enable sound manipulation at a small scale.…”

Micro-Electro-Mechanical Systems Microphones: A Brief Review Emphasizing Recent Advances in Audible Spectrum Applications

“…Subsequently, in 2022, Kumar et al [ 10 ] presented a comprehensive literature on piezoelectric microphones, along with the fabrication processes and methodologies used for experimentations. Thereafter, Gemelli et al [ 11 ] summarized some of the state-of-the-art scenarios, presenting the recent performance advances.…”