Microphone Array With Time Delay Circuits For Feedback Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sound reinforcement systems face challenges with feedback and directional issues due to the difficulty in distinguishing between direct and feedback acoustic waves, leading to howling and distortion, especially in complex environments with strong background noise.
Innovation Solution
A sound receiving device with a longitudinal linear array of microphones and time delay circuits, where microphones are spaced at specific intervals based on a center frequency, enhancing forward acoustic wave gain while inhibiting oblique waves through precise phase alignment and delay times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single microphone with enhanced directional characteristic (cardioid or super cardioid) is used to reduce feedback from the back, then feedback from the back is inhibited, but feedback from above, below, left or right still causes interference and the directional response varies with frequency
Solution Approach 1:
The patent divides a single microphone into multiple microphones arranged in an array (at least three microphones). Each microphone captures sound from different spatial positions, and through signal processing combining outputs from all microphones, the system achieves omnidirectional rejection capability while maintaining frequency response consistency, solving the limitation of single-microphone directional patterns.
Solution Approach 2:
The patent combines outputs from multiple microphones through signal processing (summation with phase adjustment). By merging the signals from multiple spatially distributed microphones and adjusting their phases, the system creates a combined output that rejects feedback from all directions while maintaining consistent frequency response, overcoming the directional limitations of individual microphones.
2Adaptability or versatility
If a sound reinforcement system uses multiple sound pickup devices to cover complex environments, then coverage is improved, but regulation and adjustment becomes rather complex
Solution Approach 1:
The patent segments the sound pickup function into multiple microphones with fixed spatial arrangement, where each microphone handles a specific spatial zone. This segmentation allows the system to cover complex environments effectively while keeping individual microphone settings simple and uniform, reducing overall regulation complexity.
Solution Approach 2:
The patent creates a universal sound pickup device that can handle multiple functions: it picks up direct sound from various directions, rejects feedback from all directions, and maintains consistent frequency response across different operating conditions. This multi-functionality eliminates the need for multiple specialized devices and simplifies system regulation.
3Volume of moving object
If microphones are placed closer together to reduce device size, then compactness is improved, but the ability to distinguish direct sound from feedback sound deteriorates
Solution Approach 1:
The patent optimizes the spacing parameter between microphones to a specific value (d = λ/2 to 2λ, where λ is the wavelength of the target frequency). This parameter optimization ensures that even with compact dimensions, the microphones maintain sufficient spatial separation to distinguish direct sound from feedback sound through phase difference analysis, achieving both compactness and discrimination capability.
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 device achieves increased gain for forward acoustic waves, reduced output for oblique waves, and stable directivity, simplifying system regulation and operation in noisy environments with strong feedback, while maintaining consistent performance across adjacent frequencies.
Implementation Method 1
a first microphone M1 and a second microphone M2 in the microphone array respectively receive a same acoustic signal
Implementation Method 2
an i-th time delay circuit has a delay time Ti defined by adding a (n−i) times of unit time to a delay time of a last time delay circuit, where said unit time is a time for an acoustic signal with a frequency set at a given center frequency to travel between two adjacent microphones
Data Source
AI summary
A sound receiving device includes a microphone array, a plurality of time delay circuits and a sound-mixing output device. The microphone array includes a plurality of microphones longitudinally arranged along a straight line in order, an output terminal of each microphone is connected with a time delay circuit, and an output terminal of the time delay circuit is connected to an input terminal of the sound-mixing output device; and an i-th time delay circuit has a delay time Ti defined by adding a (n−i) times of unit time to a delay time of a last time delay circuit. The device can increase the output of the forward acoustic wave actuation, decrease the output of the oblique acoustic wave within a certain frequency bandwidth, and obtain nearly the same directional characteristic at the central frequency and adjacent frequencies.