Key Value Indicators Intro | MEMS Microphone Guide Ep04 | Mosomic

Summary

This episode on MEMS microphones delves into the factors that determine their value, moving beyond just key performance indicators (KPIs) like noise, frequency response, and distortion. The episode introduces key value indicators (KVIs), which also account for accuracy, stability, robustness, and reliability. Key topics include the electrical, mechanical, and environmental robustness of microphones, as well as their ability to withstand disturbances like power supply noise and electrostatic discharges. The episode provides an overview of 18 KVIs, including sensitivity, phase delay, distortion, dynamic range, and immunity to external factors. Detailed discussions of each factor will follow in later episodes.

Takeaways

• 😀 MEMS microphones' value is determined not only by performance but also by their reliability, robustness, and accuracy.
• 😀 Key performance indicators (KPIs) for MEMS microphones include noise, frequency response, and distortion, but they don't capture the full value for device designers and manufacturers.
• 😀 The term 'Key Value Indicators' (KVIs) expands on KPIs by adding critical parameters like robustness, stability, and accuracy.
• 😀 Electrical robustness refers to the microphone's immunity to radio frequency disturbances, power supply noise, ESD, and other electrical disturbances.
• 😀 Mechanical robustness describes the microphone's ability to withstand physical handling and abuse without malfunctioning.
• 😀 Environmental robustness covers immunity to external factors such as moisture, temperature changes, dust, and liquids.
• 😀 Short-term accuracy ensures no performance changes due to factors like temperature, humidity, or air pressure, while long-term accuracy ensures stable performance over time.
• 😀 Sensitivity indicates the microphone's efficiency in converting sound into an electrical signal, with units in decibels (dB) or volts per Pascal.
• 😀 Total harmonic distortion (THD) quantifies the distortion in the microphone's output signal, crucial for understanding sound fidelity.
• 😀 The microphone's dynamic range and acoustic overall point (AOP) help assess its ability to handle varying sound levels without distortion.
• 😀 Power supply rejection ratio (PSRR) measures the microphone's immunity to disturbances in its power supply, while RF and ESD immunity assess its resistance to radio frequency and electrostatic discharges.
• 😀 Mechanical and environmental robustness are crucial for ensuring a microphone can endure real-world conditions without performance degradation.

Q & A

What are Key Performance Indicators (KPIs) in relation to MEMS microphones?

Key Performance Indicators (KPIs) are factors that determine the performance level of a MEMS microphone, such as signal-to-noise ratio, frequency response, and distortion. These are critical to assessing how well the microphone performs in various conditions.

What is the difference between Key Performance Indicators (KPIs) and Key Value Indicators (KVIs)?

While KPIs focus on performance parameters like noise and frequency response, Key Value Indicators (KVIs) also include reliability factors such as accuracy, stability, robustness, and longevity. KVIs are essential for device manufacturers to evaluate the microphone's overall value, particularly for its long-term use and performance consistency.

Why is accuracy and stability important in MEMS microphones?

Accuracy and stability are crucial because microphones must maintain consistent performance over time and under varying conditions. In multi-microphone systems, small changes in microphone output can significantly impact the accuracy of algorithms interpreting those signals, which can lead to malfunction or a poor user experience.

What does electrical robustness refer to in MEMS microphones?

Electrical robustness describes a microphone's ability to resist disturbances like radio frequency interference (RFI), power supply noise, and electrostatic discharge (ESD). A microphone with high electrical robustness ensures stable performance even in electrically noisy environments.

What is the significance of mechanical robustness in MEMS microphones?

Mechanical robustness indicates the microphone's capacity to withstand physical handling, abuse, and environmental conditions without malfunctioning or altering its output characteristics. This is essential for microphones used in portable or rugged devices.

How does environmental robustness impact the performance of MEMS microphones?

Environmental robustness is the microphone's immunity to environmental factors such as moisture, temperature fluctuations, dust, and other elements. This robustness ensures that the microphone continues to function correctly in a variety of challenging conditions.

What is the difference between short-term and long-term accuracy in MEMS microphones?

Short-term accuracy ensures that there are no changes in the microphone's characteristics due to factors like temperature or humidity in the short term. Long-term accuracy means that the microphone maintains consistent performance over its entire lifespan, ensuring reliability in long-term use.

What does 'sensitivity' mean in the context of MEMS microphones?

Sensitivity refers to a microphone's ability to convert sound into an electrical output signal. It is measured in decibels (dB) or volts per Pascal (for analog microphones), and decibels relative to full-scale digital signals (for digital microphones).

What is 'directivity' in MEMS microphones, and how is it measured?

Directivity refers to the microphone's sensitivity to sound from different directions. It is typically represented with a polar plot showing how sensitivity varies across 360 degrees, which helps determine whether the microphone is omnidirectional or directional.

How is the 'signal-to-noise ratio' (SNR) important for MEMS microphones?

Signal-to-noise ratio (SNR) compares the level of desired sound (signal) to the background noise generated by the microphone. A higher SNR means the microphone captures clearer audio, as the self-generated noise is minimal in relation to the actual sound.