Microphone Arrangement Spherical Transducer Positioning
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Solution Overview
Problem
Soundfield microphones face challenges in maintaining optimal frequency response and directional characteristics due to deviations from coincidence requirements, leading to distortions and artifacts, especially at higher frequencies, and are sensitive to acoustic shadowing and non-ideal mounting conditions.
Innovation Solution
The microphone arrangement positions pressure gradient transducers within an imaginary sphere with their acoustic centers close to each other, ensuring coincidence and minimizing shadowing effects by having sound inlet openings on both the front and back of the diaphragm, allowing for improved directional characteristics and frequency response through equalization and signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure gradient transducers are positioned closer together to satisfy coincidence requirements, then frequency response accuracy improves, but acoustic shadowing effects increase
Solution Approach 1:
The patent positions transducers on a spherical surface rather than a flat plane, utilizing three-dimensional spatial arrangement. This spherical geometry allows transducers to be distributed in multiple dimensions, reducing mutual acoustic shadowing while maintaining close proximity for coincidence satisfaction. The spherical coordinate system enables optimal positioning that plane arrangements cannot achieve.
Solution Approach 2:
The patent introduces a spherical reference surface as an intermediary geometric construct. This sphere serves as a mediator that defines the spatial relationships between transducers, allowing precise positioning that simultaneously achieves coincidence requirements and minimizes shadowing. The sphere's curvature provides natural spacing that prevents direct acoustic blocking between transducers.
2Reliability
If transducers are arranged in a tetrahedral configuration, then directional characteristics improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies that transducers be positioned within a spherical zone rather than at exact tetrahedral vertices. This parameter change from precise point positioning to zone positioning relaxes manufacturing tolerances while maintaining the essential tetrahedral geometric relationships. The spherical zone definition provides a practical manufacturing target that is less stringent than exact coordinate specifications.
Solution Approach 2:
The patent employs a spherical surface to define transducer positions, replacing flat-plane coordinates with curved surface geometry. This spherical arrangement naturally provides the tetrahedral angular relationships needed for directional accuracy while the curvature of the sphere facilitates manufacturing by providing a consistent reference surface. The sphere's geometry inherently maintains equidistant relationships from the acoustic center.
3Adaptability or versatility
If sound inlet openings are positioned on both front and back of diaphragm, then directional control improves, but device complexity increases
Solution Approach 1:
The patent designs each pressure gradient transducer to serve multiple functions: the same diaphragm structure with front and back sound inlet openings provides both omnidirectional pressure sensing and directional gradient sensing. This multi-functionality eliminates the need for separate transducer types for different directional requirements, reducing overall system complexity despite the enhanced capabilities of individual transducers.
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 configuration enhances the coincidence of transducers, reduces distortions, and maintains optimal frequency response across the audible range, while minimizing the impact of acoustic shadowing and mounting issues, resulting in improved recording quality and directional control.
Implementation Method 1
pressure gradient transducers having an acoustic center, a first sound inlet opening leading to a front of a diaphragm, and a second sound inlet opening leading the back of the diaphragm
Data Source
AI summary
A microphone arrangement includes multiple pressure gradient transducers having an acoustic center, a first sound inlet opening leading to a front of a diaphragm, and a second sound inlet opening leading the back of the diaphragm. A directional characteristic of the pressure gradient transducers includes an omni portion and a figure-eight portion. The pressure gradient transducers have a direction of maximum sensitivity in a main direction. Each main direction of the pressure gradient transducers is inclined. The acoustic center of a pressure transducer and the pressure gradient transducers are positioned within an imaginary sphere having a radius that corresponds to double the largest dimension of the diaphragm of one of the transducers.