Linear Differential Directional Microphone Array Design
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Solution Overview
Problem
Conventional linear differential microphone arrays (LDMA) designs face challenges with low white noise gain, especially at low frequencies, and degradation of directivity factor at high frequencies, due to their reliance on omni-directional microphones, leading to white noise amplification and deformation of beampatterns.
Innovation Solution
The design of a linear differential directional microphone array (LDDMA) that utilizes directional microphones, such as cardioid or dipole elements, to enhance beamforming performance by incorporating a microphone response matrix that accounts for the directionality of the microphones, allowing for improved white noise gain and directivity index across various frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LDMA designs use omni-directional microphones, then the array structure is simple, but the white noise gain is low especially at low frequencies causing white noise amplification
Solution Approach 1:
The patent changes the fundamental parameter of microphone directionality from omni-directional to directional (cardioid or super-cardioid). This parameter change fundamentally alters the microphone response characteristics, providing inherent noise rejection capabilities that significantly improve white noise gain, especially at low frequencies where conventional omni-directional LDMA designs suffer from white noise amplification.
Solution Approach 2:
The patent creates a composite microphone array system by integrating directional microphone elements with specific beamforming algorithms. The combination of directional microphones (which provide inherent spatial filtering) with optimized beamforming weights creates a composite system that achieves superior white noise gain compared to simple omni-directional microphone arrays.
2Reliability
If conventional LDMA designs use omni-directional microphones, then the array configuration is simple, but the directivity factor degrades as frequency increases and beampattern deforms at high frequencies
Solution Approach 1:
The patent changes the microphone response characteristic parameter from omni-directional to directional. This parameter change provides inherent high-frequency performance improvement because directional microphones have frequency response characteristics that maintain better directivity factor at high frequencies, preventing the degradation and beampattern deformation that plagues conventional omni-directional LDMA designs.
3Reliability
If more microphone elements are used to improve white noise gain with minimum-norm solution, then the array complexity increases, but the white noise gain remains relatively low at low frequencies
Solution Approach 1:
The patent changes the microphone type parameter from omni-directional to directional, which fundamentally improves white noise gain without requiring increased array complexity. The inherent directional characteristics of the microphones provide noise rejection that works effectively even with a small number of elements, making the minimum-norm solution much more effective at low frequencies.
Data Source
AI summary
Apparatus and method provided herein are directed to a linear differential directional microphone array (LDDMA), which takes into account the directionality of the array elements. The LDDMA may be designed by generating a steering vector for a linear array (LA) having preselected parameters including parameters δ, p, θ, N, and M, generating a constraint matrix based on the steering vector, reformulating the constraint matrix based on a microphone response matrix and a steering matrix, obtaining a beamformer by applying a minimum norm solution in terms of the constraint matrix, verifying a desired characteristic of the LA by calculating the beamformer for a desired direction, and constructing the LA based on the preselected parameters and the beamformer.