Active Noise Suppression via Velocity-Based Iterative Control
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Solution Overview
Problem
Existing active noise suppression systems face challenges in effectively minimizing sound from multiple primary sound sources due to limitations in sensor distribution, environmental changes, and the complexity of energy-based control methods, which often result in noise amplification in certain areas and fail to account for interactions between sound sources.
Innovation Solution
A method that iteratively determines manipulated variables for secondary sound sources to minimize sound intensity by considering the sound velocities and pressures of both primary and secondary sources, allowing for effective suppression of sound from multiple primary sources without pre-equalization, while accounting for phase changes and interactions between sound sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sound pressure-based control is used to minimize sound pressure at microphone positions, then local noise reduction is achieved, but noise amplification occurs in other areas
Solution Approach 1:
The patent replaces sound pressure-based control with sound velocity-based control. Instead of measuring and controlling sound pressure at microphone positions, the system measures sound velocity directly at the sound sources using laser Doppler vibrometry or acceleration sensors, and controls the secondary sound sources based on sound velocity signals. This substitution eliminates the fundamental problem of noise amplification in other areas while achieving global noise reduction.
Solution Approach 2:
The patent introduces sound velocity as an intermediary parameter between the primary sound sources and the control system. By measuring sound velocity at the sound sources and using it as the basis for control, the system avoids directly controlling sound pressure in the sound field, thereby preventing noise amplification in areas away from the control zones.
2Measurement precision
If global noise reduction is achieved through sound pressure-based control, then microphones must be distributed globally, but this increases system complexity and limits applicability
Solution Approach 1:
The patent extracts the control measurement from the sound field (where microphones would be distributed globally) and places it directly at the sound sources. By measuring sound velocity at the primary sound sources using laser Doppler vibrometry or acceleration sensors, the system eliminates the need for global microphone distribution while achieving global noise reduction.
Solution Approach 2:
The patent replaces the mechanical microphone-based sound pressure measurement system with a non-contact or direct-source sound velocity measurement system. This substitution dramatically reduces system complexity by eliminating the need for distributed microphones and complex calibration procedures, while enabling global noise reduction.
3Loss of energy
If energy-based control methods are used to minimize radiated sound power, then global noise reduction is achieved, but the control complexity and hardware requirements increase significantly
Solution Approach 1:
The patent extracts the essential control parameter (sound velocity) directly from the sound sources, avoiding the need for complex energy-based measurements. By measuring sound velocity at the sources and controlling secondary sources based on velocity signals, the system achieves global noise reduction with simpler hardware and control algorithms compared to full energy-based methods.
Solution Approach 2:
The patent substitutes complex energy-based control (requiring sound intensity sensors and multi-channel designs) with sound velocity-based control using simpler sensors. This substitution maintains the global noise reduction effectiveness while significantly reducing hardware complexity and control system requirements.
4Measurement precision
If secondary sound sources are used to reduce primary sound, then sound field influence is achieved, but the contribution of secondary sources may negatively overcompensate
Solution Approach 1:
The patent implements iterative feedback control where the sound velocity of secondary sound sources is determined based on the sound velocity of primary sources and the sound velocities of other secondary sources. This feedback mechanism ensures that the contribution of each secondary source is optimized to avoid negative overcompensation while achieving cumulative noise reduction across all control zones.
Solution Approach 2:
The patent employs dynamic, iterative determination of control parameters rather than static control. The manipulated variables for secondary sound sources are updated iteratively based on current sound velocity measurements and the contributions of other secondary sources, allowing the system to adapt and avoid negative overcompensation in real-time.
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
This approach enables efficient and adaptive noise suppression, reducing sound intensity to zero and minimizing the total radiated sound energy, while avoiding noise amplification in other areas and accounting for changing environmental conditions.
Implementation Method 1
The desired influencing of the sound field can be based on various physical mechanisms. In addition to the best-known case of destructive interference... One or more error microphones as sensors, each of which locally measures the sound pressure generated by all existing sound sources... The measurement results are processed by the control device, which then controls the secondary sound sources in such a way that the sound pressure at the microphones is minimized as much as possible by destructive interference
Implementation Method 2
One or more error microphones as sensors, each of which locally measures the sound pressure generated by all existing sound sources... determining a sound velocity of each primary sound source, determining a sound velocity and a sound pressure of each secondary sound source
Data Source
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Figure 3
AI summary
Disclosed and claimed is a method for the active suppression of noise from a plurality of primary noise sources by means of noise from a plurality of secondary noise sources, wherein a manipulated variable for the control of the secondary noise sources is iteratively calculated by means of: determining a velocity of each primary noise source; determining a velocity and an acoustic pressure of each secondary noise source; determining a velocity that is to be effectively suppressed for each secondary noise source, wherein the velocity that is to be effectively suppressed of a secondary noise source comprises, in addition to the velocity that has been determined for the primary noise source associated with the respective secondary noise source, also the acoustic pressures and velocities determined for the remaining secondary noise sources; determining the manipulated variable for each secondary noise source in such a way that a difference from the velocity that is to be effectively suppressed determined for one secondary noise source and the velocity determined for said one secondary noise source is minimised, and the secondary noise sources are controlled by means of the respective manipulated variables. Also disclosed and claimed is a system for the active suppression of noise by means of the method according to the invention.