Portable ELF Microphone Sealed Backchamber Infrasound Detection
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Solution Overview
Problem
Existing infrasound detection systems are large and non-portable, struggling to effectively detect very low intensity infrasound signals due to high resistance and noise interference, limiting their deployment and ability to determine signal direction.
Innovation Solution
A portable extremely low frequency electret microphone with a sealed backchamber and critically damped membrane, combined with a compact windscreen that reduces wind noise and enhances pressure amplitude transmission, allowing for sensitive infrasound detection and direction determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional microphones are used for infrasound detection, then detection capability is provided, but the systems become large and non-portable
Solution Approach 1:
The microphone system is divided into separate functional modules: a compact electret microphone unit, a windscreen assembly, and a signal processing system. This segmentation allows the core detection function to be miniaturized while maintaining portability without sacrificing detection capability through modular design.
Solution Approach 2:
The patent changes the electrical parameters of the microphone by using electret technology instead of conventional condenser microphones, eliminating the need for high polarization voltages and reducing the overall device size. This parameter change enables portable deployment while maintaining infrasound detection sensitivity.
2Measurement precision
If high sensitivity microphones are used to detect weak infrasound signals, then detection sensitivity is improved, but resistance and noise interference increase
Solution Approach 1:
The windscreen, which initially might be seen as an obstruction, is designed to convert harmful wind noise into beneficial pressure amplitude enhancement for infrasound signals. The windscreen structure creates a pressure differential that amplifies the weak infrasound signals while blocking higher frequency wind noise, thereby improving detection sensitivity without increasing noise interference.
Solution Approach 2:
The windscreen acts as an intermediary element between the external environment and the microphone sensor. It mediates the interaction by filtering out harmful wind noise while allowing and enhancing the pressure amplitude of infrasound signals, thus protecting the sensitive microphone from direct exposure to wind interference.
3Adaptability or versatility
If conventional microphones are used, then infrasound detection is provided, but the systems lack portability for various deployment applications
Solution Approach 1:
The compact microphone system is designed with universal applicability for multiple deployment scenarios including unmanned aerial vehicles, space missions, and ground-based monitoring. The standardized, miniaturized design allows the same core system to be adapted to different platforms and applications, enhancing versatility without requiring large, application-specific systems.
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 system achieves high sensitivity and portability, capable of detecting infrasound signals with frequencies below 20 Hz, overcoming the limitations of conventional microphones and enabling deployment in various applications, including unmanned aerial vehicles and space missions.
Implementation Method 1
In condenser and electret microphones, the transduction mechanism is based upon changes in the stored electric field energy. In a condenser microphone (also termed an air-condenser microphone), acoustic energy causes small movement of the microphone diaphragm (also termed a membrane), which serves as one plate of a parallel-plate capacitor.
Implementation Method 2
The backchamber is sealed to allow substantially no air exchange between the backchamber and outside the microphone.
Implementation Method 3
a compact windscreen that reduces wind noise and enhances pressure amplitude transmission
Data Source
AI summary
The present invention is an extremely low frequency (ELF) microphone and acoustic measurement system capable of infrasound detection in a portable and easily deployable form factor. In one embodiment of the invention, an extremely low frequency electret microphone comprises a membrane, a backplate, and a backchamber. The backchamber is sealed to allow substantially no air exchange between the backchamber and outside the microphone. Compliance of the membrane may be less than ambient air compliance. The backplate may define a plurality of holes and a slot may be defined between an outer diameter of the backplate and an inner wall of the microphone. The locations and sizes of the holes, the size of the slot, and the volume of the backchamber may be selected such that membrane motion is substantially critically damped.