MEMS Micro-Speaker Shutter for Bass Sound Pressure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS micro-speakers face challenges in achieving high sound pressure levels, particularly for acoustic bass frequencies, due to limitations in their design and functionality.
Innovation Solution
The speaker device incorporates a transducer element and a laterally offset shutter element in the housing, where the shutter element is movable and driven by an actuation signal with half the frequency of the transducer element, enabling ultrasonic demodulation and reducing squeeze film damping, thus enhancing sound pressure levels across the frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional MEMS micro-speaker design is used, then the device size is reduced, but the sound pressure level is insufficient, especially for bass frequencies
Solution Approach 1:
The shutter element is designed to be movable rather than fixed, allowing it to dynamically modulate the acoustic output signal from the transducer element. The shutter portion moves in response to the demodulation signal to vary the acoustic impedance in the acoustic path, enabling ultrasonic demodulation that extracts bass frequencies while maintaining compact device dimensions
Solution Approach 2:
The shutter element acts as an intermediary component between the transducer element and the acoustic aperture. It modulates the ultrasonic signal from the transducer by varying acoustic impedance, effectively demodulating the signal to produce audible bass frequencies without requiring a larger device structure
2Device complexity
If the shutter element is positioned close to the transducer element, then the device complexity is reduced, but squeeze film damping increases
Solution Approach 1:
The shutter element is positioned laterally offset from the transducer element rather than directly adjacent to it. This asymmetric arrangement creates a lateral displacement that reduces the severity of squeeze film damping effects while maintaining a relatively simple overall device structure with fewer components
3Stress or pressure
If ultrasonic demodulation is implemented, then bass frequency output is improved, but the device requires additional components
Solution Approach 1:
The shutter element serves multiple functions: it acts as an acoustic impedance modulator for ultrasonic demodulation, functions as a shutter to control acoustic flow, and works in conjunction with the transducer element to produce both ultrasonic and audible frequency outputs. This multi-functionality enables bass frequency enhancement without requiring separate dedicated components for each function
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 allows for improved sound pressure levels, reduced power consumption, and a more compact design, effectively addressing the limitations of conventional MEMS micro-speakers, especially in producing bass frequencies.
Implementation Method 1
the first actuation signal has an ultrasonic signal component which is modulated with an audio signal component
Implementation Method 2
reducing squeeze film damping, thus enhancing sound pressure levels
Data Source
AI summary
A speaker device comprises a housing having an acoustic aperture, a transducer element in the housing configured to receive a first actuation signal and to generate an acoustic output signal. The speaker device comprises a shutter element in the housing configured to receive a second actuation signal and arranged laterally offset to the transducer in the housing. The shutter element is arranged in an acoustic path between the transducer element and the acoustic aperture and comprises a shutter portion movable in opposite directions in response to the second actuation signal. A controller provides the first actuation signal to the transducer element, while the first actuation signal has an ultrasonic signal component modulated with an audio signal component. The controller provides the second actuation signal to the shutter element that has half the frequency of the ultrasonic signal component.