Sound Pressure Gradient Microphone Phase Control
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Solution Overview
Problem
Conventional sound pressure gradient microphones experience variations in gain and phase, leading to a 'Dip' in sound pressure gradient output, particularly at low frequencies, which complicates achieving favorable frequency characteristics and directivity.
Innovation Solution
The implementation of a sound pressure gradient microphone configuration that includes a first and second non-directional microphone, a delay device, and a subtractor, where the phase of the first non-directional microphone is ahead of the second, utilizing high-pass filters or digital filters to ensure the phase of the signal output from the first is ahead of the second, thereby preventing the 'Dip' in frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sound pressure gradient microphone configuration is used, then directivity characteristics can be obtained, but 'Dip' occurs in frequency characteristics at low frequencies
Solution Approach 1:
The patent changes the phase relationship parameter between the two non-directional microphones. Specifically, it configures the phase of the first non-directional microphone to be ahead of the phase of the second non-directional microphone, which prevents the Dip phenomenon in frequency characteristics while maintaining directivity. This parameter change resolves the contradiction by adjusting the phase relationship rather than changing the basic microphone configuration.
2Reliability
If phase control is implemented to prevent Dip, then frequency characteristics improve, but device complexity increases
Solution Approach 1:
The patent implements preliminary phase control by configuring the first non-directional microphone to have its phase ahead of the second non-directional microphone before signal processing. This preliminary phase arrangement is built into the microphone configuration itself, allowing the system to prevent Dip without requiring complex real-time phase adjustment mechanisms during operation.
Solution Approach 2:
The patent uses two non-directional microphones that are essentially copies of the same microphone type, but with a deliberate phase difference introduced between them. By using identical microphone elements with a controlled phase relationship, the system achieves the desired frequency characteristics without needing complex different microphone designs or additional phase correction hardware.
Data Source
AI summary
A sound pressure gradient microphone includes: a first non-directional microphone; a second non-directional microphone; a delay device that receives an output of the second non-directional microphone; and a subtractor that receives an output of the first non-directional microphone and an output of the delay device. The subtractor outputs a difference between the output of the first non-directional microphone and the output of the delay device. A phase of the first non-directional microphone is ahead of a phase of the second non-directional microphone.