Wide Dynamic Range Microphone With Dual Transducer Switching
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Solution Overview
Problem
MEMS microphones have a limited dynamic range, restricting their application scope due to the difference between the weakest and strongest audio signals they can accurately reproduce, which is a result of noise floor limitations at the lower end and distortion at the higher end of their dynamic range.
Innovation Solution
A microphone system with multiple transducers, each having a unique dynamic range that overlaps with others, allowing the system to selectively couple outputs based on sound pressure levels, thereby extending the overall dynamic range and enabling accurate reproduction of a wider range of audio signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single transducer is used, then the device complexity is low, but the dynamic range is limited
Solution Approach 1:
The microphone system is divided into multiple transducers, each optimized for specific sound pressure ranges. The first transducer handles low sound pressure levels while the second transducer handles high sound pressure levels, allowing the system to achieve extended dynamic range by segmenting the overall function across multiple specialized components.
Solution Approach 2:
The system dynamically switches between different transducers based on the incident sound pressure level. A selector circuit automatically couples the appropriate transducer output to the system output depending on whether the sound pressure is low or high, enabling the system to adapt its configuration in real-time to match the input conditions.
2Measurement precision
If multiple transducers with overlapping dynamic ranges are used, then the overall dynamic range is extended, but the device complexity increases
Solution Approach 1:
A selector circuit acts as an intermediary between the multiple transducer outputs and the system output. This intermediary component automatically routes the appropriate transducer output based on sound pressure level detection, managing the complexity of multiple sources by using a simple switching mechanism rather than complex signal processing.
Solution Approach 2:
The system uses the output signals from the transducers themselves to determine which transducer should be selected. By monitoring the sound pressure level through the transducer outputs, the system makes its own selection without requiring external control or complex processing, allowing the signals to essentially self-direct the switching decision.
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 effectively captures a broader range of sound pressures by switching between transducers, reducing noise and distortion, and providing a seamless transition to maintain signal fidelity across varying sound levels.
Implementation Method 1
Condenser MEMS microphones typically have a diaphragm that forms a capacitor with an underlying backplate. 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.