Programmable MEMS Microphone Response for Wind Noise Attenuation
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Solution Overview
Problem
Condenser microphones, particularly MEMS microphones, face issues with signal clipping and distortion due to high-amplitude acoustic signals, such as wind buffets, which exceed the diaphragm's displacement limit or overwhelm processing circuitry, leading to loss of signal content.
Innovation Solution
A microphone system with a transducer and two circuits: the first circuit processes the electrical signal from the transducer, and the second circuit automatically detects predetermined criteria (frequency or amplitude-dependent) to couple an impedance to the first circuit, attenuating unwanted signals by connecting a capacitor or resistor, thereby preventing signal overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the diaphragm displacement limit is exceeded due to high-amplitude acoustic signals, then the microphone can handle loud sounds, but signal clipping and distortion occur causing loss of signal content
Solution Approach 1:
The feedback circuit generates an anti-phase signal that preemptively counteracts the harmful high-amplitude components before they cause clipping and distortion in the output signal, thereby preventing signal content loss
Solution Approach 2:
The system uses a feedback circuit that monitors the output signal and dynamically adjusts the feedback amount based on detected signal characteristics, enabling automatic suppression of clipping and distortion while preserving signal integrity
2Object-affected harmful factors
If the feedback amount is increased to suppress unwanted frequencies, then signal clipping is prevented, but the complexity of the circuit increases
Solution Approach 1:
The feedback circuit automatically detects signal characteristics and self-adjusts the feedback amount without external control, simplifying the overall system while effectively suppressing unwanted frequencies
Solution Approach 2:
The system dynamically changes the feedback parameter (feedback amount) based on real-time signal analysis, enabling adaptive suppression of harmful frequencies without requiring complex fixed circuitry
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
Effectively attenuates unwanted high-energy frequencies, preventing signal clipping and maintaining signal quality by dynamically adjusting the impedance to manage signal amplitudes and frequencies, ensuring the processing circuit is not overwhelmed.
Implementation Method 1
The capacitance of the capacitor varies rapidly as the distance between the diaphragm and the plate varies due to the vibration of the diaphragm
Implementation Method 2
The diaphragm and the conductive plate collectively form a capacitor. An electrical charge is placed on the capacitor, typically by an associated circuit. The capacitance of the capacitor varies rapidly as the distance between the diaphragm and the plate varies due to the vibration of the diaphragm
Data Source
AI summary
Methods and apparatus automatically cancel or attenuate an unwanted signal (such as low frequencies from wind buffets) from, and/or control frequency response of, a condenser microphone, or control the effective condenser microphone sensitivity before the signal reaches an ASIC or other processing circuit. As a result, the maximum amplitude signal seen by the processing circuit is limited, thereby preventing overloading the input of the processing circuit. Remaining (wanted) frequencies can be appropriately amplified to reduce the noise burden on further processing circuits. A corrective signal is applied to a bias terminal of the condenser microphone to cancel the unwanted signal. Optionally or alternatively, a controllable impedance is connected to a line that carries the signal generated by the MEMS microphone, so as to attenuate unwanted portions of the signal.