Shape Memory Alloy Acoustic Valve for Earbud Seal Control
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Solution Overview
Problem
Portable electronic devices with low-profile transducers, such as in-ear earbuds, face challenges in maintaining optimal sound quality due to improper seals with the ear canal, leading to discomfort and lower sound quality, especially during physical activities.
Innovation Solution
An acoustic valve actuated by shape memory alloy (SMA) actuators with a bowstring configuration and a bistable spring mechanism, allowing for dynamic control of sound impedance and seal between the device and the ear canal, featuring zero holding power and minimal energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a low-profile transducer is used in an in-ear electronic device, then the device can be made compact and portable, but the sound quality deteriorates due to improper seal with the ear canal
Solution Approach 1:
The patent applies a dynamic seal mechanism that can change its state between open and closed positions. The resilient seal member is biased to engage with the ear canal wall to form a seal, but can be actuated to disengage and open the acoustic passage. This dynamic adjustment allows the device to maintain both compact size and reliable sound quality by adapting the seal strength to different usage conditions.
2Reliability
If an in-ear device extends into the ear canal to achieve better performance, then sound quality improves, but discomfort and pressure increase due to improper seal
Solution Approach 1:
The dynamic seal mechanism allows the device to adjust the seal strength by transitioning between closed and open positions. When the seal is too strong causing discomfort, the system can actuate to open the passage, reducing pressure on the ear canal wall while maintaining adequate seal for sound quality when needed.
Solution Approach 2:
The patent changes the acoustic impedance parameter by adjusting the seal state. The resilient seal member can be positioned to create different levels of occlusion in the ear canal, thereby dynamically adjusting the acoustic load on the transducer and the pressure exerted on the ear canal, optimizing both sound quality and comfort.
3Force
If a traditional electromagnetic actuator is used to control the acoustic valve, then sufficient force can be generated, but the device size increases and packaging becomes difficult
Solution Approach 1:
The patent replaces the traditional electromagnetic actuator with a shape memory alloy (SMA) actuator. The SMA wire generates sufficient force to actuate the lever mechanism and move the seal member between open and closed positions. This substitution dramatically reduces the actuator size, allowing the acoustic valve to be packaged into a compact in-ear device while maintaining adequate actuation force.
4Stability of the object's composition
If a valve mechanism with holding power is used to maintain valve state, then stable positioning is achieved, but energy consumption increases
Solution Approach 1:
The patent employs a resilient seal member with built-in elasticity that provides self-holding capability. The seal member is biased by a spring or resilient material to automatically return to and maintain the closed position when the actuating force is removed. This self-service mechanism eliminates the need for continuous power consumption to maintain the valve state, as the elastic restoration force naturally holds the seal in position without active control.
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 SMA-actuated valve maintains optimal sound quality by adjusting acoustic impedance, reducing discomfort, and minimizing energy use, while providing a comfortable fit during various activities.
Implementation Method 1
Upon cooling, the shape memory alloy wire transforms from austenite to martensite and contracts, which can be used to actuate the valve to the closed position
Implementation Method 2
Upon heating, the shape memory alloy wire transforms from martensite to austenite and expands, which can be used to actuate the valve to the open position
Implementation Method 3
a bistable spring or flexure may also be used to actuate the valve and provide zero holding power in the open or closed position. For example, the bistable spring or flexure may be a resilient flexure attached to the piston of the valve that both mounts and guides the valve piston
Data Source
AI summary
An in-ear electronic device comprising: an enclosure having an enclosure wall that defines an interior chamber surrounding a transducer and an opening from the interior chamber to an ambient environment surrounding the enclosure; and an acoustic valve comprising a driven member coupled to a driving member having a lever and a shape memory alloy operable to cause the driven member to open and close the opening upon application of a current.