MEMS Sound Transducer Acoustic Waveguide for Structure-Borne Noise
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Solution Overview
Problem
Existing sound transducer systems face challenges in miniaturization, acoustic quality, energy efficiency, electromagnetic compatibility, and complex assembly, particularly in implementing effective active noise cancellation (ANC) due to structure-borne sound coupling and design limitations.
Innovation Solution
A microelectromechanical sound transducer system with a MEMS-based sound generating device featuring a cavity between a planar cover and base, equipped with movable actuators and strategically positioned microphones to minimize structure-borne sound coupling, allowing for efficient sound emission and reception while implementing ANC functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If sound transducers are integrated in a compact space for miniaturization, then device size is reduced, but structure-borne sound coupling increases and acoustic quality deteriorates
Solution Approach 1:
The patent extracts the harmful structure-borne sound coupling by introducing a dedicated acoustic coupling element (acoustic waveguide) that separates the acoustic path from the mechanical structure. This acoustic waveguide acts as an intermediary channel that carries sound waves from the transducer to the microphone without transmitting structure-borne vibrations, thereby eliminating the harmful coupling effect while maintaining compact integration.
Solution Approach 2:
The acoustic waveguide serves as an intermediary element between the sound transducer and the microphone. It mediates the acoustic signal transmission by providing a dedicated pathway that is acoustically coupled to the transducer output but mechanically isolated from the device housing, thus enabling sound transmission while blocking structure-borne noise propagation.
2Adaptability or versatility
If multiple sound transducers are assembled individually to form sound transducer systems, then functional requirements are met, but assembly complexity increases as device size decreases
Solution Approach 1:
The patent merges the sound transducer and microphone into a single integrated housing structure. The sound transducer is mounted on the inner surface of the housing while the microphone is positioned within the same housing, eliminating the need for separate assembly steps. This integration reduces assembly complexity while maintaining the functional requirements of both sound generation and detection.
Solution Approach 2:
The housing structure serves multiple functions simultaneously: it provides mechanical support for both the sound transducer and microphone, creates the acoustic coupling pathway, and isolates structure-borne noise. This multi-functionality reduces the overall system complexity by consolidating multiple components into a single structural element.
3Volume of moving object
If acoustic path length is reduced for miniaturization, then device size is reduced, but phase difference optimization for ANC performance becomes difficult
Solution Approach 1:
The patent employs dynamic positioning of the microphone within the housing, allowing adjustment of the microphone's location relative to the sound transducer. This dynamic configuration enables optimization of the acoustic path length and phase difference for ANC performance, even while maintaining a compact overall device size. The system can adapt the acoustic pathway geometry to achieve optimal phase relationships.
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
The solution enables improved miniaturization, reduced structure-borne sound coupling, and enhanced ANC performance by optimizing the acoustic path and phase difference between actuation and feedback signals, resulting in improved sound quality and stability.
Implementation Method 1
MEMS-based sound transducer devices can use different mechanisms for sound generation. For example, piezoelectric sound transducers, electrostatically driven sound transducers, etc. are available as MEMS-based devices
Implementation Method 2
The actuators are movable in a plane that is perpendicular to the thickness direction of the sound generating device. The sound pressure generated by the actuators in the cavity exits through one or more openings or through holes in the cover and/or base.
Implementation Method 3
a microphone mounted on or integrated in the cover, wherein the microphone is positioned adjacent to at least one sound outlet opening of the cover
Implementation Method 4
The microelectromechanical sound transducer system implements active noise cancellation (ANC) functions in order to improve the sound quality of the sound transducer system by applying a cancellation signal that is to compensate for the ambient noise.
Data Source
AI summary
This invention relates to a microelectromechanical loudspeaker implemented as a system-on-chip or system-in-package. The microelectromechanical loudspeaker includes a microelectromechanical sound-generating device implemented in a microelectromechanical system (MEMS) and a microphone mounted on the cover or integrated in the cover, wherein the microphone is positioned adjacent to one of the sound outlet openings of the cover. The MEMS comprises a cavity formed between a planar cover, a planar base and circumferential sidewalls provided between the cover and the base. The MEMS further comprises a plurality of movable actuators for generating sound. The actuators are provided in the cavity between the cover and the base, and wherein the cover and the base have a plurality of sound outlet openings to emit sound in a direction transverse to the cover and the base, respectively.