Dipole Microphone Array Feedback Suppression
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Solution Overview
Problem
Existing transducers for acoustic instruments and voice applications face challenges in effectively suppressing uncontrolled acoustic feedback while maintaining high fidelity, as they often fail to distinguish between nearfield sound sources and farfield noise, leading to instability and degraded sound quality.
Innovation Solution
A dipole microphone array with closely spaced microphones, where each microphone pair is out of phase and precisely balanced, is used to suppress feedback by creating a null plane that cancels farfield sounds while enhancing nearfield sound sources, with optional baffle and orientation adjustments for improved frequency response and feedback suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional microphones or vibration sensors are used to capture acoustic guitar sound, then the sound fidelity is maintained, but acoustic feedback from the amplifier and loudspeaker cannot be effectively suppressed
Solution Approach 1:
The system segments the audio signal processing into multiple independent microphone channels, each capturing sound from different spatial positions. By processing these segmented spatial signals separately and then combining them with appropriate time delays, the system can selectively enhance desired frequencies while suppressing feedback frequencies, thereby resolving the contradiction between maintaining sound fidelity and suppressing acoustic feedback.
Solution Approach 2:
The system dynamically adjusts the time delay parameters for each microphone channel based on the spatial position of the microphone relative to the sound source and feedback path. This dynamic parameter adjustment allows the system to adaptively optimize the frequency response, enhancing desired sounds while suppressing feedback, thus improving both sound quality and system stability.
2Object-affected harmful factors
If microphone separation distance is increased to suppress feedback frequencies, then feedback suppression is improved, but new feedback frequencies are created and sound fidelity is degraded
Solution Approach 1:
The system changes the key parameter of microphone separation distance to optimize performance. By carefully selecting separation distances that are not integer multiples of the wavelength of feedback frequencies, the system avoids creating new feedback while still suppressing existing feedback. This parameter optimization allows the system to achieve feedback suppression without degrading sound fidelity.
Solution Approach 2:
The system dynamically adjusts time delay parameters for each microphone channel to compensate for the spatial separation. By introducing appropriate time delays, the system can align the desired sound components while maintaining the spatial separation needed for feedback suppression, thus preserving sound fidelity while achieving feedback suppression.
3Power
If amplifier gain is increased to improve sound output, then sound quality is enhanced, but acoustic feedback oscillation occurs
Solution Approach 1:
The system uses feedback suppression techniques by analyzing the acoustic feedback path and introducing counter-phase signals to cancel feedback frequencies. This allows the amplifier gain to be increased for better sound output while the feedback suppression mechanism prevents oscillation, effectively resolving the contradiction between power output and feedback 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 dipole microphone array significantly reduces uncontrolled acoustic feedback, maintains high fidelity for nearfield sound sources, and achieves effective suppression of farfield noise, allowing for increased amplifier gain without feedback oscillations, thus enhancing sound quality and stability.
Implementation Method 1
The dipole microphone array (DMA) exploits this close proximity to enhance sensitivity to the acoustic waves from the vibrating strings and sound hole of the guitar while suppressing sounds from sources further away, such as a loudspeaker reproducing the acoustic guitar sounds
Implementation Method 2
Some embodiments include a small baffle in the array, and diffraction over this baffle further improves performance
Data Source
AI summary
A dipole microphone assembly for a nearfield sound source has a first microphone and a second microphone. The second microphone is out of phase with the first microphone so as to provide a dipole microphone assembly. Each of the microphones has a port, and a dipole spacing is defined as a distance from the center of the port of the first microphone to the center of the port of the second microphone. The dipole spacing is less than ¼ of a wavelength for the highest frequency of the sound of interest.