Narrow Directional Stereo Microphone Using Unidirectional Units
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Solution Overview
Problem
Conventional mid-side stereo microphones require a bidirectional microphone unit and a matrix circuit, increasing cost and complexity, while also potentially failing to achieve optimal bidirectionality without an optimum design.
Innovation Solution
A narrow directional stereo microphone design that replaces the bidirectional microphone unit with two unidirectional microphone units, symmetrically disposed relative to the microphone body's major axis, eliminating the need for a matrix circuit by directly connecting the mid microphone unit's signals to the unidirectional units for stereo signal generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bidirectional microphone unit is used in the mid-side stereo microphone, then the stereo signal separation is achieved, but the cost and device complexity increase
Solution Approach 1:
The bidirectional microphone unit is segmented into two separate unidirectional microphone units (first and second unidirectional microphone units). Each unidirectional unit captures sound from a specific direction, and their outputs are combined to achieve the stereo effect that would otherwise require a single bidirectional unit, thereby reducing complexity while maintaining functionality.
Solution Approach 2:
The outputs of the two unidirectional microphone units are merged through the matrix circuit to produce the side signal. By combining the signals from two simpler unidirectional microphones positioned at specific angles, the system achieves the bidirectional capture capability needed for MS stereo recording without using a single complex bidirectional microphone unit.
2Reliability
If a matrix circuit is added to achieve stereo signal processing, then the stereo signal separation is improved, but the device complexity and cost increase
Solution Approach 1:
The matrix circuit performs multiple functions: it processes signals from both unidirectional microphone units, applies appropriate weighting and phase shifting, and generates both the mid and side signals required for MS stereo recording. This multi-functional approach achieves complete stereo signal separation using a single integrated circuit rather than multiple separate processing stages.
3Reliability
If a bidirectional microphone unit is used, then the echolocation capability is maintained, but the manufacturing precision requirements increase
Solution Approach 1:
Instead of requiring uniform bidirectional characteristics from a single microphone unit, the system uses two unidirectional microphone units with specific directional characteristics. Each unit is optimized for its specific capture direction, and their combined output achieves the desired echolocation capability. This approach allows for more relaxed manufacturing tolerances on individual units while maintaining overall system performance.
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
This design reduces costs and complexity by eliminating the need for a bidirectional microphone unit and matrix circuit, while maintaining effective stereo signal separation and frequency characteristics, albeit at the cost of reduced echolocation capability.
Implementation Method 1
The mid microphone unit 20 includes a diaphragm 201 and a fixed electrode 202 opposed to each other at an appropriate space so as to define a capacitor. The side microphone unit 30 also includes a diaphragm 301 and a fixed electrode 302 defining a capacitor. The diaphragms 201 and 301 vibrate upon receiving sound waves, and their distances from the fixed electrodes 202 and 302 vary, leading to variations in capacitance. Such variations in capacitance are output from the fixed electrodes 202 and 302 as sound signals.
Data Source
AI summary
A narrow directional stereo microphone includes a narrow directional mid unit disposed such that the directional axis thereof aligns to the major axis of a microphone body, and a unidirectional right unit and a unidirectional left unit disposed symmetrically with respect to the major axis such that directional axes of the right and left units are perpendicular to the major axis, wherein signals output from the mid unit are sent to one of a diaphragm and a fixed electrode of the right unit and to one of a diaphragm and a fixed electrode of the left unit, and right channel signals are output from the other of the diaphragm and the fixed electrode of the right unit, and left channel signals are output from the other of the diaphragm and the fixed electrode of the left unit.