MEMS Speaker Crossover Architecture for Full Audio Band Coverage
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Solution Overview
Problem
Micro Electro Mechanical System (MEMS) speakers typically employ a single membrane type, limiting design flexibility and sound quality by restricting the maximum input frequency to around 15-17 KHz, which is insufficient for covering the entire audible range.
Innovation Solution
A sound producing device comprising multiple MEMS sound producing cells with different membranes and resonance frequencies, driven by specific audio bands, and a crossover circuit that partitions the input signal into complementary frequency bands to optimize sound production across the audible range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single membrane type is used in MEMS speakers, then the device structure is simple and manufacturing is easier, but the maximum input frequency is limited to around 15-17 KHz and design flexibility is reduced
Solution Approach 1:
The audio frequency range is segmented into multiple bands, with each band handled by a dedicated sound producing cell with membranes optimized for that specific frequency range. This allows the system to cover a broader frequency spectrum while maintaining manufacturing simplicity for each individual membrane type.
Solution Approach 2:
Multiple membrane types are integrated into a single speaker device, where each membrane is designed for specific frequency ranges. This multi-functional approach enables the speaker to handle different audio bands effectively, expanding the overall frequency coverage beyond what a single membrane could achieve.
2Adaptability or versatility
If multiple MEMS sound producing cells with different resonance frequencies are used, then the frequency range and sound quality are improved, but the device complexity increases
Solution Approach 1:
The speaker is divided into multiple sound producing cells, each responsible for a specific audio band. This segmentation allows optimization of each cell for its designated frequency range while maintaining manageable complexity through modular design and systematic signal distribution.
3Productivity
If the resonance frequency of the membrane is closer to the maximum driving signal frequency, then the membrane displacement efficiency increases, but the power consumption increases and distortion occurs
Solution Approach 1:
Each sound producing cell uses membranes with resonance frequencies locally optimized for its specific audio band. This local optimization ensures high displacement efficiency for each frequency range while avoiding the need to drive membranes far from their resonance frequencies, thereby reducing overall power consumption and distortion.
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
Enhances design flexibility and sound quality by effectively covering the entire audible range, reducing power consumption, and mitigating discrepancies between in-ear and free-field speakers, while maintaining efficient membrane displacement and sound pressure levels.
Implementation Method 1
a first sound producing cell comprising a first membrane, driven by a first driving signal, configured to produce a first acoustic sound on a first audio band
Implementation Method 2
a first resonance frequency of the first membrane is higher than the first maximum frequency of the first driving signal
Data Source
AI summary
A sound producing device includes a first sound producing cell, driven by a first driving signal and configured to produce a first acoustic sound on a first audio band, and a second sound producing cell, driven by a second driving signal and configured to produce a second acoustic sound on a second audio band different from the first audio band. A first membrane of the first sound producing cell and a second membrane of the second sound producing cell are Micro Electro Mechanical System fabricated membranes. The first audio band is upper bounded by a first maximum frequency; the second audio band is upper bounded by a second maximum frequency. A first resonance frequency of the first membrane is higher than the first maximum frequency of the first driving signal. A second resonance frequency of the second membrane is higher than the second maximum frequency of the second driving signal.