Dual-Transducer Micro-Speaker Venting for Low-Distortion Audio
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Solution Overview
Problem
Existing micro-speakers in ear-worn hearing devices suffer from distortion of the acoustic audio signal due to non-linear effects of modulating the ultrasonic carrier wave, limiting their performance and integration in compact devices.
Innovation Solution
The micro-speakers incorporate a first and second acoustic transducer with an acoustic conduit and a vent between the conduit and an exterior air space, where the second transducer modulates the acoustic wave and an acoustic vent reduces impedance, minimizing distortion by maintaining consistent impedance regardless of transducer operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a shutter is used to modulate the ultrasonic carrier wave in a micro-speaker, then an acoustic audio signal can be produced, but the acoustic signal becomes distorted due to non-linear effects
Solution Approach 1:
A compliant member is introduced as an intermediary element between the shutter and the ultrasonic carrier wave modulation process. This compliant member absorbs and compensates for non-linear effects, acting as a mediator that maintains linear acoustic signal output while allowing the shutter to perform its modulation function. The compliant member deforms in response to pressure changes, smoothing out distortions that would otherwise occur during the modulation process.
2Volume of moving object
If the acoustic aperture is made smaller to reduce device size, then the micro-speaker can be integrated in compact ear-worn devices, but the acoustic impedance becomes highly non-linear
Solution Approach 1:
The compliant member changes its physical parameters (deformation, stiffness) in response to varying pressure conditions. As the shutter moves and pressure changes occur, the compliant member dynamically adjusts its mechanical properties to maintain linear acoustic impedance. This parameter change allows the system to achieve linear performance with a small acoustic aperture, enabling compact device integration without sacrificing signal quality.
3Device complexity
If the acoustic impedance varies with transducer operation, then the micro-speaker can be compact, but the acoustic signal distortion increases
Solution Approach 1:
The compliant member serves as a mediator between the variable impedance environment and the acoustic signal path. It decouples the impedance variations caused by transducer operation from the acoustic output, ensuring that signal fidelity is maintained despite the compact device architecture. The compliant member's mechanical compliance allows it to absorb impedance variations while maintaining a stable acoustic interface.
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 configuration reduces acoustic signal distortion, enhancing sound quality and enabling efficient integration in compact ear-worn devices like TWS earphones and hearing aids.
Implementation Method 1
A first acoustic transducer generates an ultrasonic carrier wave between a first opening of the body member and a first exterior medium
Implementation Method 2
A second acoustic transducer modulates the ultrasonic carrier wave between a second opening of the body member and a second exterior medium to produce an acoustic audio signal
Implementation Method 3
An acoustic vent between the acoustic conduit and an exterior air space reduces acoustic impedance, minimizing distortion
Data Source
AI summary
A micro-speaker for use in hearing and other body worn devices is disclosed, including an acoustic conduit defining an acoustic path between first and second air spaces. A first acoustic transducer is located between the acoustic conduit and the first air space and a second acoustic transducer located between the acoustic conduit and the second air space. The second acoustic transducer is operable to more or less obstruct an acoustic aperture between the acoustic conduit and the second air space, wherein concurrent operation of the first and second acoustic transducers generates an acoustic audio signal that propagates between the first and second air spaces. An acoustic vent between the acoustic conduit and the second air space has an acoustic impedance that is independent of the operation of the second acoustic transducer.