MEMS Sound Transducer With Segmented Membrane and Dual Drive
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Solution Overview
Problem
Micro loudspeakers face challenges in achieving high sound pressure levels, especially at low frequencies, due to limited deflection volume and surface area, which affects their performance in both free-field and confined applications, and they struggle with energy efficiency and distortion, particularly in miniaturized devices like headphones and hearing aids.
Innovation Solution
A MEMS sound transducer integrating a substrate with an electrodynamically controllable membrane and a piezoelectrically controlled bending actuator, allowing for a two-way drive system that combines electrodynamic and piezoelectric drives to enhance sound pressure levels and frequency response, with the membrane divided into parts by thin gaps for high deflectability and reduced distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the active surface area of the membrane is increased to achieve higher sound pressure levels, then the sound pressure level improves, but the device dimensions and complexity increase
Solution Approach 1:
The membrane is divided into multiple segments separated by thin gaps, allowing each segment to deflect independently with high amplitude. This segmentation enables the membrane to achieve large effective displaced volume without increasing the overall device footprint, as the gaps between segments can be minimized while maintaining high deflectability of each individual segment
Solution Approach 2:
The membrane segments are designed to be highly dynamic with large deflection capabilities through the thin gap structure. The dynamic deflection of multiple segments creates a cumulative effect that generates high sound pressure levels without requiring a large static membrane area, as each segment contributes to the overall acoustic output through its motion
2Stress or pressure
If the membrane deflection volume is increased to improve low frequency sound pressure, then the sound pressure level at low frequencies improves, but the device size increases
Solution Approach 1:
By segmenting the membrane into multiple independently deflecting parts separated by thin gaps, the system achieves large effective deflection volume through the cumulative motion of multiple segments rather than requiring a single large-deflection membrane. This allows high low-frequency sound pressure generation within compact dimensions
Solution Approach 2:
The thin gap structure fundamentally changes the deflection parameter by enabling much larger angular displacements and deflection volumes without increasing the membrane's planar footprint. This parameter change allows the membrane to displace sufficient air volume for high sound pressure generation while maintaining small device dimensions
3Device complexity
If a single drive system is used to simplify the device structure, then the device complexity decreases, but the frequency response and sound pressure level across the frequency range are limited
Solution Approach 1:
The patent merges electrodynamic and piezoelectric drive systems into a single integrated membrane structure, where each drive type controls specific membrane segments. This combination leverages the high force output of electrodynamic actuators and the precision control of piezoelectric actuators to achieve superior frequency response and sound pressure levels across the entire audible range while maintaining a unified device architecture
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables higher sound pressure levels across the frequency range, particularly at low frequencies, improved energy efficiency, and reduced distortion, optimizing performance for both in-ear and free-field applications while enabling miniaturization and high-volume production.
Implementation Method 1
a membrane (14) which is connected to at least one integrated permanent magnet (14p) and is electrodynamically controllable
Implementation Method 2
a bending actuator (16) which is applied onto the membrane (14) and can be piezoelectrically controlled separately from the membrane (14)
Data Source
AI summary
A MEMS sound transducer includes a substrate, a membrane formed within the substrate, and a bending actuator applied onto the membrane. The membrane includes at least one integrated permanent magnet and is electrodynamically controllable. The bending actuator can be piezoelectrically controlled separately from the membrane.