Active Noise Reduction via Energy-Based Control
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Solution Overview
Problem
Existing active noise reduction systems face challenges in achieving global noise reduction due to limitations in sound pressure-based controls, which often result in noise amplification in other areas and are not effective in minimizing sound power radiation from primary sound sources, and energy-based controls are complex and lack practical implementation solutions.
Innovation Solution
A method and system that utilize energy-based control by measuring physical quantities like acceleration of the primary sound source, transforming these measurements into the frequency domain, and adjusting a secondary sound source to oscillate in phase or opposition with the primary source to minimize effective sound power radiation, using a simplified hardware setup with a reference sensor, sound pressure sensor, and a control device to generate a time-dependent control signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing 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 energy-based control. Instead of measuring and controlling sound pressure at specific points using microphones, the system measures the actual energy (sound power) radiated by the primary sound source and controls the secondary sound source to minimize this energy. This substitution of the control basis from pressure to energy resolves the contradiction by directly targeting the harmful energy radiation rather than local pressure variations that cause amplification elsewhere.
Solution Approach 2:
The patent introduces a new measurement intermediary - an energy measurement sensor that directly measures the sound power radiated by the primary sound source. This intermediary provides accurate energy information that enables the control system to minimize radiated energy without causing noise amplification, bridging the gap between the primary sound source and the control objective.
2Manufacturing precision
If sound pressure-based control with globally distributed microphones is used for global noise reduction, then global sound pressure minimization is achieved, but system complexity and installation effort increase
Solution Approach 1:
The patent extracts the essential measurement function from a complex array of globally distributed microphones and concentrates it into a single energy measurement sensor placed near the primary sound source. This extraction eliminates the need for multiple microphones distributed throughout the space, significantly reducing system complexity while maintaining global noise reduction effectiveness.
Solution Approach 2:
The energy measurement sensor serves multiple functions: it directly measures the sound power radiated by the primary source, provides information for controlling the secondary sound source, and enables global noise reduction without requiring a complex microphone array. This multi-functionality simplifies the overall system architecture.
3Manufacturing precision
If energy-based control is used to minimize radiated sound power, then global noise reduction is achieved, but hardware complexity and control complexity increase
Solution Approach 1:
The patent replaces complex multi-channel energy measurement hardware with a simplified sensor setup that directly measures sound power. The control algorithm is simplified by using energy-based feedback instead of complex sound pressure field control, reducing both hardware and control complexity while achieving global noise reduction.
4Manufacturing precision
If secondary sound sources are used to reduce primary sound via destructive interference, then sound reduction is achieved at control points, but the ability of sound sources to radiate sound is reduced
Solution Approach 1:
The patent introduces an energy measurement sensor as an intermediary that directly measures the sound power radiated by the primary sound source. This measurement enables the control system to optimize the secondary sound source's operation to minimize energy radiation through mutual influence, rather than relying solely on destructive interference at specific points. The intermediary provides the feedback necessary to achieve energy minimization while managing the trade-off in radiation ability.
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 achieves a significant global reduction in sound pressure levels, particularly for stationary noise sources, with a simple and adaptable system that is insensitive to environmental changes and can be universally applied, reducing noise by up to 8 dB in specific scenarios.
Implementation Method 1
The control device controls the loudspeakers on the basis of the signals supplied by the sensors in such a way that the entire sound field generated by the combination of the primary sound source and the loudspeakers is favorably influenced in terms of the goal of sound reduction. One or more sensors can be used to generate reference signals, on the basis of which control signals for the secondary sound sources are determined
Data Source
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AI summary
The method involves measuring a physical parameter with a reference sensor (2) dependent on time for the primary sound source (1), which characterizes the sound-generating motion of the emitting surface of the primary sound source. The corresponding time-dependent reference parameters (q-pq-t) are obtained, which comprise the phase information of the primary sound source. The secondary sound source (6) is controlled with a time-dependent driving signal. An independent claim is also included for an active noise reduction system for active noise reduction of a sound field generated by a swinging emitting surface of a primary sound source.