Interferometric Microphone Calibrator Reducing Calibration Uncertainty
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Solution Overview
Problem
Conventional microphone calibration methods, such as the reciprocity method, are complex, time-consuming, and have high uncertainties, while laser-based interferometry has not replaced standard calibration techniques effectively for secondary calibrations, necessitating a more efficient and accurate method for determining microphone sensitivity.
Innovation Solution
An interferometric microphone calibrator and process that uses an interferometer to produce and receive measurement light, allowing for the comparison calibration of a test microphone against a reference microphone, reducing uncertainty and simplifying the calibration process by determining sensitivity through interferometer backscattered light analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional reciprocity method is used for microphone calibration, then calibration can be performed, but the process becomes complex and time-consuming with high uncertainties
Solution Approach 1:
The patent replaces the conventional mechanical/electrical reciprocity calibration system with an optical interferometry system. The interferometer uses light waves to directly measure diaphragm displacement, eliminating the need for complex electrical signal routing and mechanical coupling required by reciprocity methods. This substitution of optical measurement for electrical/mechanical measurement reduces both process complexity and uncertainty.
Solution Approach 2:
The patent extracts the core measurement function from the complex reciprocity calibration process by using interferometry to directly measure diaphragm displacement. This extraction isolates the essential measurement (diaphragm motion) from the cumbersome electrical signal processing and mechanical coupling requirements, achieving simpler and more precise calibration.
2Measurement precision
If conventional reciprocity method is used for microphone calibration, then calibration can be performed, but the process takes significant time
Solution Approach 1:
The optical interferometry system measures diaphragm displacement directly through light wave interference, eliminating the time-consuming electrical signal generation, transmission, and measurement steps required by reciprocity methods. The interferometer provides real-time displacement data, dramatically reducing calibration time while maintaining or improving accuracy.
Solution Approach 2:
The interferometer continuously tracks diaphragm displacement throughout the calibration process, providing uninterrupted measurement data. This continuous optical measurement eliminates the discrete measurement steps and signal processing delays inherent in conventional methods, achieving both faster and more accurate sensitivity determination.
3Productivity
If laser-based interferometry is used for secondary calibration, then measurement speed improves, but the method has not effectively replaced standard techniques due to remaining challenges
Solution Approach 1:
The patent implements feedback by using the interferometer to continuously monitor diaphragm displacement and comparing this measurement against the expected motion from the known acoustic signal. This feedback loop validates the calibration process in real-time, building confidence in the method's reliability and enabling it to replace conventional techniques. The feedback mechanism ensures measurement accuracy while maintaining high speed.
Solution Approach 2:
The interferometer acts as an intermediary between the acoustic field and the measurement system, translating diaphragm mechanical motion into optical interference patterns that can be precisely measured. This intermediary optical measurement system bridges the gap between the acoustic calibration process and quantitative measurement, providing both speed and reliability that enables widespread adoption.
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 method provides significantly reduced uncertainty and is quicker and easier than conventional secondary calibration techniques, achieving accurate sensitivity determination of test microphones relative to reference microphones, with expanded uncertainties of ±0.05 dB at 250 Hz and 1000 Hz, demonstrating good agreement with reciprocity method results.
Implementation Method 1
an interferometer in optical communication with a microphone and that produces an interferometer measurement light, communicates the interferometer measurement light to the microphone, and receives an interferometer backscattered light from the microphone
Implementation Method 2
receives an interferometer backscattered light from the microphone
Implementation Method 3
subjecting the reference microphone to an electrical waveform from the preamplifier-controller; moving the reference microphone diaphragm according to the electrical waveform; producing, by the reference microphone diaphragm, an acoustic wave comprising an amplitude and frequency from the electrical waveform
Data Source
AI summary
An interferometric microphone calibrator for comparison calibrating a microphone, the interferometric microphone calibrator comprising: an interferometer in optical communication with a microphone and that produces an interferometer measurement light, communicates the interferometer measurement light to the microphone, and receives an interferometer backscattered light from the microphone, such that a sensitivity of a test microphone is interferometrically calibrated to a reference microphone from the interferometer backscattered light; a preamplifier-controller in electrical communication with the microphone, and that receives a driver signal from a microphone driver and drives the microphone driver; the microphone driver in electrical communication with the preamplifier-controller and that receives a driver control signal from a calibration controller and produces the driver signal based on the driver control signal; and a calibration controller in electrical communication with the microphone driver and that produces the driver control signal and communicates the driver control signal to the microphone driver.