MEMS Microphone: Ultimate Guide to its Basic Working Principle, Applications & Advantages

Microelectromechanical systems (MEMS) are the newest technology that replaces the conventional electret condenser microphone (ECM). MEMS microphone works by converting sound pressure into an electric signal.

Microphones come in all shapes and sizes. From the tiny microphones in your ear buds to the large ones in studio-quality recording equipment, they all have one purpose: to convert sound waves into electrical signals that our audio devices can understand.

In this article, we’ll take a look at MEMS microphone, one of the newest types of microphones on the market. MEMS stands for Micro electromechanical Systems, and these microphones are quickly becoming the industry standard for portable audio devices.

Take a look at some other articles that might be interesting before diving deep into the topic

Table of Contents

What Is A MEMS Microphone?

MEMS stands for Microelectromechanical systems (MEMS) and this is the newest technology that replace conventional electret condenser microphone (ECM). Basic principle of MEMS is to convert sound pressure into electric signal.

The MEMS microphone is manufactured using micro-electromechanical systems processing techniques. It is composed of a moving diaphragm and a stationary perforated backplate. This arrangement mimics the design of a condenser microphone, and is etched directly onto the silicon wafer.

Like a condenser microphone, a MEMS mic is typically mounted on a circuit board and can be connected to an audio preamp or other application-specific components.
It has small size, low cost, less sensitive, and better noise cancellation performance.

It is the best substitute for electret condenser microphones (ECM) and commonly used in laptops, smartphones and tablets.

In the past, traditional electret condenser microphones were used in many small consumer products. These mics were made using a single diaphragm and a stationary plate. The diaphragm and the stationary plate interacted to create a capacitor.

How Does a MEMS Microphone Work? Basic Principle

MEMS has three main parts:

Transducer: include polysilicon diaphragm and dual-backplates act as electrodes.
Application specific integrated circuit (ASIC): that measure capacitance.
Dual membranes: that reduce noise by creating vacuum between membranes.

Design and Modeling of a MEMS Dual-Backplate Capacitive Microphone with Spring-Supported Diaphragm for Mobile Device Applications elaborated the advance structure and basic working principle of MEMS microphines. According to it, this microphone has a dual-backplates that allow sound pressure to move to polysilicon diaphragm. Polysilicon diaphragm convert it into an electrical signal using a bias voltage. The transducer converts the mechanical energy of the diaphragm into an electric output.

The microphone is often used in recording and communication devices. It can also be used to measure sound pressure and its magnitude. The microphone is often used in acoustic and vibration sensors.

The MEMS mic is often used in applications such as cell phones, hearing aids, and security alarms. MEMS mic designs are based on a variety of semiconductor technologies, including bulk silicon, silicon on insulator (SOI), silicon on sapphire (SOS), and silicon on glass (SOG).

Application of MEMS Microphones

MEMS microphones are a new type of digital microphone. They are built in tiny packages with volumes that are less than 7.5 mm. Because of their small size, they are ideal for a variety of applications.

In the world of professional audio equipment, MEMS microphones are used for their excellent sensitivity and high-resolution sound. The following are some of the uses of MEMS in audio devices.
Applications Include:

Smartphones
Tablets
Laptops
Hearing Aids
Voice Biometric
Digital Voice Assistants
Automotive vehicles
Digital cameras
Medical devices

The transduction principle of MEMS microphones is based on coupled capacitance change. The sound moves the membrane and modulates the air gap between the two conductive plates. An acoustic resonator is formed by a ventilation hole in the microphone. As a result, the frequency of the sound generated by the device is monitored. The data from this signal is used to identify potential problems with equipment and perform preventative maintenance. This can save a lot of money and time by reducing the risk of an expensive shutdown.

In comparison to traditional ECMs, MEMS microphones can reach more than 130 dBSPL without generating any distortion. In addition to their low noise sensitivity, they are very versatile and can be used for recording audio signals. ACMs also have a higher frequency response. A good example is a microphone with a notch filter.

In addition, MEMS mics are being used in industrial applications. For example, NASA’s Jet Propulsion Laboratory is using MEMS mics to detect the impact of meteors. Other uses include monitoring the environment inside the human body and detecting air pollution. MEMS mics have been in use for over 20 years. They are being used in more and more applications today. In the last few years, however, the use of MEMS mics has increased dramatically. This trend may be due to MEMS mics’ ability to be manufactured in very small sizes. This, in turn, allows for the manufacturing of very small, inexpensive, and portable devices.

MEMS Microphones vs. Electret Condenser Microphones

So what’s the difference between a MEMS microphone and a traditional electret condenser microphone

Are they the same thing?

Condenser microphones (ECM microphones) utilize capacitor charge/discharge that generates vibrations that are measured by signal transmission. While MEMS microphone employ semiconductor technology base on the principle of converting sound pressure into electric signal.

In the past, traditional electret condenser microphones were used in many small consumer products. These mics were made using a single diaphragm and a stationary plate.

The diaphragm and the stationary plate interacted to create a capacitor. The diaphragm was usually made of a thin, flexible membrane that was etched behind a perforated plate. As sound waves passed through the diaphragm, the diaphragm flexed, which allowed the sound to reach the stationary plate and create a change in capacitance.

The MEMS microphone designed is largely based on the design of the electret condenser microphone capsule.

Both mic types include the following design details. Work on electrostatic principles. Capacitor-based capsules with one movable plate (diaphragm) and one stationary plate. A method of permanently charging the capsule (ASIC or electret material.

Both these mic types are also very common and typically used in consumer and professional electronics that require microphones.

In particular, we’ll discuss the benefits each microphone type has over the other.

Starting with the typical MEMS microphone:

Smaller size Analog PCB and ADC incorporated within the package Lower-impedance (much better for noisy environments)More resistant to mechanical vibration MEMS microphone technology is being developed rapidly.

And now for electret condenser microphones:

Many legacy designs have electret microphone capsules ECM connections include pins, wires, SMT, solder pads and spring contacts which makes them much more flexible for design within various applications Better protection from dust and moisture, partly due to their larger physical size.
ECM products are available with intrinsic directionality, including omnidirectional, bidirectional, unidirectional, or even noise-cancelling Wider operating voltage range, allowing them to function with loosely regulated voltage rails Electret technology extends to professional-grade studio, measurement, and film microphones.

Advantages of MEMS Microphones

It has less sensitive over temperature fluctuation than ECMs.
It is very small and light weight.
It can be used for both wired and wireless.
It has good audio quality.
It can withstand a wide frequency range.
It has excellent noise cancellation ability.
It requires little power.
Its sound quality is natural.
It has a very low cost.
It has a low profile.
It can be integrated with other components.
It has good sound quality than ECMs.
It has excellent sensitivity and high-resolution sound.

Disadvantages of MEMS Microphones

It is expensive.
It is not rugged in nature as polysilicon is used that can not withstand high power.
It does not have high input impedance and requires high power supply.
Proper training is required to operate MEMS microphones.

Conclusion

Today, in the era of artificial intelligence, we are seeing new MEMS design strategies that use innovative automated optimization techniques. For example, a group at the Institute for Electronic Design Automation at the Technical University of Munich has studied and demonstrated the automated optimization of a MEMS microphone design in MEMS+.

We hope to discuss this fascinating topic at further length in a future blog post.