Dual-Transducer Microphone Switching for Wide Dynamic Range
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Solution Overview
Problem
MEMS microphones have a limited dynamic range, restricting their application due to the difference between the weakest and strongest audio signals they can accurately reproduce, which leads to noise floor issues at low sound pressures and distortion at high sound pressures.
Innovation Solution
A microphone system with multiple transducers, each with its own dynamic range, is designed to overlap and selectively couple outputs based on sound pressure levels, allowing for a wider dynamic range and improved signal reproduction by switching between transducers or combining their outputs, such as through a weighted sum or cross-fade method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transducer is used, then the device complexity is low, but the dynamic range is limited
Solution Approach 1:
The patent combines multiple transducers (first transducer with low bottom-end dynamic range and second transducer with high top-end dynamic range) into a single microphone system. The outputs of these transducers are combined through a summing node to create an overall system dynamic range that extends from the lowest detectable signal of the first transducer to the highest detectable signal of the second transducer, effectively merging their individual capabilities into a unified system.
Solution Approach 2:
The microphone system achieves multi-functionality by enabling a single device to accurately transduce audio signals across a wide range of sound pressure levels. The system can handle both low sound pressure signals (using the first transducer) and high sound pressure signals (using the second transducer), making it universally applicable to diverse acoustic environments without requiring multiple separate microphones.
2Adaptability or versatility
If multiple transducers with overlapping dynamic ranges are used, then the dynamic range is extended, but the device complexity increases
Solution Approach 1:
The patent segments the dynamic range coverage by using multiple transducers, each optimized for specific sound pressure levels. The first transducer is optimized for low sound pressure levels with a low bottom-end, while the second transducer is optimized for high sound pressure levels with a high top-end. Their overlapping dynamic ranges allow for segmented coverage that collectively spans a wider overall range.
Solution Approach 2:
The system dynamically selects which transducer output to use based on the incident sound pressure level. A selector switches between the first and second transducer outputs depending on the detected sound pressure level, allowing the system to adapt dynamically to varying acoustic conditions and maintain optimal performance across the extended dynamic range.
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 extends the dynamic range of MEMS microphones, enabling accurate reproduction of a broader range of sound pressures with reduced noise and distortion, improving fidelity and adaptability to varying audio conditions.
Implementation Method 1
Receipt of an audio signal causes the diaphragm to vibrate to form a variable capacitance signal representing the audio signal
Data Source
AI summary
A microphone system has an output and at least a first transducer with a first dynamic range, a second transducer with a second dynamic range different than the first dynamic range, and coupling system to selectively couple the output of one of the first transducer or the second transducer to the system output, depending on the magnitude of the input sound signal, to produce a system with a dynamic range greater than the dynamic range of either individual transducer. A method of operating a microphone system includes detecting whether a transducer output crosses a threshold, and if so then selectively coupling another transducer's output to the system output. The threshold may change as a function of which transducer is coupled to the system output. The system and methods may also combine the outputs of more than one transducer in a weighted sum during transition from one transducer output to another, as a function of time or as a function of the amplitude of the incident audio signal. Methods of operating the system may include equalizing the outputs of two or more transducers prior to coupling one or more outputs to the system output.