Condenser Microphone Diaphragm Dual-Period Irregularity Pattern
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Solution Overview
Problem
Existing condenser microphones face challenges in achieving increased adsorption stability with respect to a fixed pole while maintaining or improving low frequency response, particularly in electret condenser microphones where partial variations in the external electric field lead to uneven diaphragm adsorption.
Innovation Solution
A diaphragm with a thermoplastic resin film featuring a combination of a first irregularity pattern with rough, long-period hexagonal tortoiseshell features and a second irregularity pattern with fine, short-period mesh features is formed, using a manufacturing process involving a heating and cooling apparatus with a mold and deformable mesh material to enhance stability and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If only fine irregularities are formed on the diaphragm, then adsorption stability increases, but low frequency response deteriorates due to excessive tension requirements
Solution Approach 1:
The irregularity pattern is segmented into two distinct types: first irregularities with a first period and second irregularities with a second period shorter than the first. This segmentation allows each type to fulfill different functions - the first irregularities provide structural support for low frequency response, while the second irregularities enhance adsorption stability through increased surface area and electrostatic interaction with the electret.
Solution Approach 2:
Different regions of the diaphragm surface are given different irregularity characteristics. The first irregularities provide a base structure with larger scale features, while the second irregularities add fine-scale features throughout. This local differentiation of surface properties enables simultaneous optimization of both low frequency response and adsorption stability across different spatial scales.
2Manufacturing precision
If tension on the diaphragm is increased to improve low frequency response, then low frequency response improves, but adsorption stability decreases
Solution Approach 1:
The dual-period irregularity structure segments the functional requirements: the first irregularities (longer period) maintain the diaphragm's mechanical integrity and low frequency response characteristics without requiring high tension, while the second irregularities (shorter period) provide the necessary adsorption stability through increased surface area and electrostatic interaction.
3Manufacturing precision
If only long period irregularities are formed, then low frequency response is maintained, but adsorption stability is insufficient
Solution Approach 1:
The irregularity system is segmented into two scale levels: first irregularities with a first period that preserve low frequency response, and second irregularities with a second period (shorter than the first) that enhance adsorption stability. The combination of these segmented structures achieves both objectives simultaneously.
Solution Approach 2:
The diaphragm surface creates a composite irregularity structure combining two different spatial frequencies. This composite structure integrates the benefits of both long-period irregularities (low frequency response) and short-period irregularities (adsorption stability), achieving a synergistic effect that neither structure could provide alone.
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 increases adsorption stability by 10-15% compared to previous designs, while maintaining or improving low frequency response, resulting in a more sensitive condenser microphone.
Implementation Method 1
The electret dielectric film has specific properties (self-polarization properties) of becoming in a polarized state due to corona discharge or the like if a DC high voltage is applied
Implementation Method 2
a polarization voltage due to electret exists between the diaphragm and the fixed pole. Therefore, an electrostatic attraction force is applied to the diaphragm
Implementation Method 3
heating the mold to a temperature capable of softening the diaphragm by using the heating means
Implementation Method 4
cooling the mold to a predetermined temperature by the cooling means
Data Source
AI summary
The adsorption stability with respect to a fixed pole is increased while the low frequency response of a diaphragm is improved especially in an electret condenser microphone. In a diaphragm 11 for a condenser microphone, which is formed of a thermoplastic resin film having a metal film on one surface thereof, a first irregularity pattern 12 consisting of rough irregularities 12a having a long period and a second irregularity pattern 13 consisting of fine irregularities 13a having a short period are formed over the whole region of the diaphragm 11.