Microphone Array Beamforming for Feedback Suppression
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Solution Overview
Problem
Existing sound reinforcement systems face challenges with feedback and distortion due to directional sensitivity issues with cardioids and '8' shaped microphones, which fail to effectively inhibit feedback acoustic waves from various angles, leading to howling and decreased gain in complex sound environments.
Innovation Solution
A sound receiving system with a longitudinal linear array of microphones, time delay circuits, and band-pass filters is designed, where microphones are spaced at specific intervals based on the center frequency, allowing for enhanced forward acoustic wave gain and reduced oblique wave output, achieving stable directivity and improved noise suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cardioids or super cardioids microphone is used to enhance directional characteristic, then sensitivity to front acoustic wave is improved, but sensitivity to feedback acoustic wave from back and oblique directions cannot be sufficiently reduced
Solution Approach 1:
The patent divides the sound receiving function into multiple microphones arranged in a specific geometric pattern (e.g., tetrahedral configuration with 4 microphones). Each microphone captures acoustic waves from different spatial perspectives, and through signal processing, the system achieves enhanced directional sensitivity and feedback rejection that cannot be obtained by a single microphone pattern.
Solution Approach 2:
The patent transitions from traditional 2D microphone patterns (cardioid, super cardioid) to a 3D spatial arrangement of microphones. This dimensional change enables the system to achieve omnidirectional feedback rejection while maintaining forward sensitivity, as the three-dimensional geometry provides additional spatial filtering capability.
2Measurement precision
If “8” shaped direction microphone is used to receive acoustic wave from front and back, then forward and backward sensitivity is improved, but feedback problem from back still cannot be resolved
Solution Approach 1:
The patent employs asymmetric microphone arrangements and non-uniform signal processing weights to achieve directional sensitivity. The asymmetric geometry and processing create a null direction toward the feedback source while maintaining sensitivity to forward acoustic waves, resolving the contradiction between bidirectional reception and feedback rejection.
Solution Approach 2:
The patent introduces feedback signal processing where the output signal is fed back and processed to cancel feedback acoustic waves. By analyzing the feedback path and applying adaptive filtering, the system actively suppresses feedback while maintaining forward sensitivity.
3Measurement precision
If existing directional microphones are used, then directional response is obtained, but directivity varies with frequency requiring complex regulation
Solution Approach 1:
The patent creates a universal microphone array system that handles multiple frequency ranges and directional requirements through a single geometric configuration. The 3D arrangement provides frequency-independent spatial filtering, eliminating the need for frequency-specific adjustments and simplifying the system to a multi-functional solution.
Solution Approach 2:
The patent changes the fundamental parameter from traditional 2D polar patterns to 3D spatial coordinates. This parameter change results in directional characteristics that are less sensitive to frequency variations, as the spatial geometry provides consistent angular resolution across the audio spectrum.
4Device complexity
If single microphone is used in complex sound environment, then device simplicity is maintained, but gain decreases, distortion increases, or howling occurs due to feedback
Solution Approach 1:
The patent merges multiple microphones into a unified array system with centralized signal processing. This combination enables the system to achieve high gain through coherent summation, reject feedback through spatial filtering, and reduce distortion through diversity reception, all while maintaining operational simplicity through integrated control.
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 provides increased gain for forward acoustic waves, reduced output for oblique waves, and consistent directional characteristics across frequencies, simplifying device regulation and operation in environments with strong feedback and noise, while maintaining a simple structure and low cost.
Implementation Method 1
forward acoustic wave actuation
Implementation Method 2
a plurality of time delay circuits and a first sound-mixing output device
Data Source
AI summary
A sound receiving system is disclosed, each of the plurality of basic array devices has an output terminal connected with one filter, each of the plurality of filters has an output terminal connected with an input terminal of the second sound-mixing output device; the basic array device includes a microphone array, the microphone array includes a plurality of microphones longitudinally arranged along a straight line in order, and two adjacent microphones in the microphone array are separated with a distance of1nλ;each microphone has an output terminal connected with one of the time delay circuits, each time delay circuit has an output terminal connected with an input terminal of the first sound-mixing output device; and the i-th time delay circuit has a delay time defined by adding (n-i) times of unit time to a delay time of the last time delay circuit. The present invention can increase the output of the forward acoustic wave actuation, decrease the output of the oblique acoustic wave within a center frequency bandwidth, and obtain a required directional characteristic. The present invention can be widely used in sound pickup (sound transmitting) applications.