Spherical Backplate Design for Condenser Microphone Pull-In Prevention
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Solution Overview
Problem
Condenser microphones often malfunction due to the diaphragm and backplate becoming infinitely close and attaching under high sound pressure, leading to reduced sound quality and increased risk of malfunction.
Innovation Solution
A backplate with a spherical surface recessed away from the diaphragm is used, increasing the pull-in voltage and maintaining a gap to prevent attachment, formed through laser machining for precise processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the diaphragm and backplate are positioned close to each other to improve sensitivity, then the sensitivity is improved, but the risk of attachment under high sound pressure increases
Solution Approach 1:
The backplate surface is designed as a spherical surface rather than a flat surface. This curvature creates a geometric relationship where the diaphragm and backplate surfaces are always separated by a minimum distance, preventing attachment even when the diaphragm vibrates under high sound pressure, while still maintaining close proximity for high sensitivity
2Reliability
If the diaphragm and backplate are positioned far apart to prevent attachment, then the reliability is improved, but the sensitivity decreases
Solution Approach 1:
The spherical surface of the backplate allows the diaphragm to be positioned very close to the backplate at most points, maximizing sensitivity, while the curvature ensures that there is always a controlled minimum distance at the center region, preventing attachment and maintaining reliability
3Ease of manufacture
If a flat backplate surface is used to simplify manufacturing, then the ease of manufacture is improved, but the occurrence of attachment under high sound pressure increases
Solution Approach 1:
The spherical surface can be manufactured with high precision using laser machining technology, which makes the manufacturing process feasible despite the increased complexity compared to flat surfaces. The curvature is essential for preventing attachment while maintaining close proximity
4Reliability
If the maximum depth at the center of the spherical surface is increased to prevent attachment, then the reliability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The spherical surface parameters (radius, depth) are optimized to achieve the right balance between preventing attachment and maintaining manufacturability. The maximum depth at the center is specifically designed to be greater than or equal to the maximum amplitude at the center of the diaphragm, ensuring reliable separation while being achievable with laser machining precision
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 design enhances the microphone's ability to withstand high sound pressure levels, improves sound quality, and reduces equivalent noise levels by increasing the pull-in voltage and maintaining a gap between the diaphragm and backplate.
Implementation Method 1
When a sound signal acts on the diaphragm, the diaphragm is forced to vibrate, so that the distance between the diaphragm and the backplate changes, which causes a change in the capacitance between the two polar plates
Implementation Method 2
the two may be infinitely close to each other and easily attached together, leading to instant malfunction of the microphone
Implementation Method 3
the spherical surface is formed by laser machining
Data Source
AI summary
The present application relates to a backplate for a recording microphone, and the recording microphone, belonging to the technical field of acoustoelectric conversion. A surface, facing a diaphragm, of the backplate is a spherical surface recessed away from the diaphragm. According to the backplate for the recording microphone and the recording microphone provided by the present application, the maximum sound pressure level that the recording microphone can withstand is effectively increased, and the occurrence of attachment between the diaphragm and the backplate under the action of high-sound-pressure-level signals is reduced.