Piezoelectric Speaker Multiple Diaphragms Low-Frequency Sound
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Solution Overview
Problem
Compact mobile devices face challenges in achieving both low-frequency and stereo sound reproduction due to restricted volumetric capacity, where increasing diaphragm size is hindered by casing constraints and the need for multiple speakers to maintain stereo performance.
Innovation Solution
A piezoelectric speaker design featuring multiple diaphragms with laminated insulating and conductive layers, connected by insulating and damping components, allowing separate voltage application and linear vibration, which increases sound pressure and supports both low-frequency and stereo reproduction within a reduced mounting space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diaphragm area is increased to improve low-frequency reproduction, then the low-frequency reproduction performance is improved, but the device size and mounting space increase
Solution Approach 1:
The patent divides a single large diaphragm into multiple smaller diaphragms (at least two) that are electrically insulated from each other. Each diaphragm is driven by separate voltages to achieve constructive interference, effectively increasing the air displacement volume for low-frequency reproduction without requiring a single large diaphragm area. This segmentation allows the speaker unit to maintain compact dimensions while achieving the required low-frequency performance.
2Reliability
If multiple speaker units are mounted to achieve stereo reproduction, then the stereo reproduction capability is improved, but the mounting space and device complexity increase
Solution Approach 1:
The patent combines multiple diaphragms and piezoelectric elements into a single integrated speaker unit that can perform both mono and stereo reproduction. The multiple diaphragms are electrically insulated and can be driven independently, allowing the unit to function as multiple speakers. This merging approach achieves stereo capability without requiring separate speaker units, thereby reducing mounting space and simplifying the overall device structure.
Solution Approach 2:
The speaker unit is designed to serve multiple functions: it can reproduce sound in mono mode using all diaphragms together, and in stereo mode by selectively activating different diaphragm combinations. This multi-functionality allows a single speaker unit to replace what would traditionally require multiple separate speakers, achieving stereo reproduction capability while maintaining compact dimensions.
3Reliability
If the diaphragm stroke is increased to improve low-frequency reproduction, then the low-frequency reproduction performance is improved, but the speaker thickness increases
Solution Approach 1:
The patent uses multiple diaphragms that can be driven in phase to achieve constructive interference, effectively increasing the air displacement volume without requiring increased stroke of individual diaphragms. By segmenting the acoustic output across multiple diaphragms rather than relying on a single diaphragm with large stroke, the design maintains thin profile while achieving improved low-frequency reproduction performance.
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 design enhances sound pressure at low frequencies and maintains stereo reproduction capabilities, even when the device is rotated, by utilizing the additional diaphragms to increase air displacement and vibration area, effectively addressing the space constraints of compact devices.
Implementation Method 1
a piezoelectric element having formed thereon an electrode of silver thin film or the like is adhered to a metal diaphragm. A sound output mechanism of the piezoelectric speaker is such that an application of an AC voltage to both surfaces of the piezoelectric element causes a generation of a shape distortion of the piezoelectric element, so that the metal diaphragm is vibrated, thereby generating a sound.
Data Source
AI summary
A piezoelectric speaker comprises a plurality of diaphragms, connecting components, and piezoelectric elements. The plurality of diaphragms are each formed by a laminated material in which a core layer made of an insulating material is laminated to skin layers each made of a conductive material so as to form the skin layers on both surfaces of the core layer. The connecting components each corresponds to a plate-shaped component of the insulating material and connects between at least two of the plurality of diaphragms. Piezoelectric elements are mounted on surfaces of the plurality of diaphragms, respectively. The plurality of diaphragms are insulated from each other such that separate voltages are applied to the piezoelectric elements mounted thereon, respectively.