Silent Zone Generation via Green's Function Noise Control
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Solution Overview
Problem
In environments like vehicle interiors, positioning microphones close to the user for superior acoustic properties is often impractical, leading to inconvenient and potentially hazardous arrangements, while existing noise cancellation systems are not effective in enhancing acoustic properties without compromising safety and convenience.
Innovation Solution
A system comprising a loudspeaker and error microphone adjacent to the listening position, a microphone array above, and a noise controller using a Green's function matrix to generate a silent zone by filtering noise signals and controlling the noise reduction transfer function based on error and noise signals, effectively creating a quiet area around the listener's head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microphones are positioned close to the user's head, then acoustic properties are improved, but convenience and safety deteriorate
Solution Approach 1:
The patent introduces an intermediary system consisting of remote microphones, loudspeakers, and signal processing electronics that mediates between the noise source and the user's head. The microphones are positioned away from the head (solving safety/convenience issues) while still capturing noise signals, and loudspeakers positioned near the head generate anti-noise signals, creating an indirect path that achieves both safety and acoustic performance.
Solution Approach 2:
The patent replaces the mechanical approach of physically positioning microphones near the head with an electronic/acoustic system. Instead of relying on physical proximity for noise capture, the system uses electronic signal processing, Green's function-based transfer function calculation, and active noise control algorithms to achieve the desired acoustic effect without mechanical proximity.
2Measurement precision
If microphones are positioned close to the user's head, then acoustic properties are improved, but safety deteriorates
Solution Approach 1:
The system uses an intermediary acoustic field generated by loudspeakers positioned near the head to deliver anti-noise signals, while microphones remain positioned safely away from the user. This intermediary approach allows the system to maintain safety while achieving the acoustic control objective through coordinated speaker-microphone positioning and signal processing.
Solution Approach 2:
The system performs preliminary action by pre-calculating transfer functions using Green's functions that model the acoustic paths from loudspeakers to the user's head. This allows the system to predict and compensate for acoustic effects before they occur, enabling safe microphone positioning while maintaining acoustic control through pre-computed compensation algorithms.
3Measurement precision
If microphones are mounted on flexible arms or booms extending toward the user, then acoustic properties are improved, but device complexity increases
Solution Approach 1:
The patent extracts the microphone function from the complex mechanical mounting structures (flexible arms, booms) and separates it from the user-proximity requirement. Microphones are positioned in fixed, safe locations away from the head, and their sole function is to capture noise signals. The complex positioning mechanism is eliminated entirely, replaced by a simpler fixed installation with electronic compensation.
Solution Approach 2:
The patent replaces the mechanical system of flexible arms and booms with an electronic/acoustic system. Instead of using mechanical positioning to achieve acoustic proximity, the system uses electronic signal processing, transfer function calculation, and active noise control to achieve the same acoustic effect with simpler, fixed mechanical structures.
4Measurement precision
If microphones are mounted on flexible arms or booms extending toward the user, then acoustic properties are improved, but user injury risk increases
Solution Approach 1:
The system introduces an intermediary acoustic field generated by loudspeakers as a safe mediator between the noise control function and the user's head. This eliminates the need for microphones to be positioned in hazardous proximity to the user, as the loudspeakers serve as the intermediary element that can be safely positioned near the head while microphones remain in safe, fixed locations.
Solution Approach 2:
The patent extracts the hazard-risk element (microphones on extended arms near the user) from the system and replaces it with a safe configuration. The microphone function is extracted from the hazardous positioning and relocated to safe, fixed positions, while the acoustic control function is achieved through a different mechanism (loudspeaker-based anti-noise generation) that does not require hazardous mechanical structures.
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 effectively generates a silent zone by radiating sound that destructively interferes with noise, enhancing acoustic properties while ensuring safety and convenience by adapting to head movements and noise sources, applicable in various environments including vehicles.
Implementation Method 1
a loudspeaker disposed adjacent to the listening position and configured to radiate sound that corresponds to a sound signal
Implementation Method 2
radiating sound that destructively interferes with noise
Implementation Method 3
an error microphone disposed adjacent to the listening position and configured to pick up noise radiated by a noise source
Implementation Method 4
a microphone array comprising a multiplicity of array microphones disposed above the listening position and configured to pick up noise
Data Source
Figure 1~3
Figure 4~5
AI summary
Generating a silent zone at a listening position includes radiating, with a loudspeaker disposed adjacent to the listening position, sound that corresponds to a sound signal, and picking up, with an error microphone disposed adjacent to the listening zone, noise radiated by a noise source via a primary path to the listening position and the sound radiated by the loudspeaker via a secondary path to the listening position, and generating a corresponding error signal. It further includes picking up, with a microphone array comprising a multiplicity of array microphones disposed above the listening position, noise radiated by a noise source via a primary path to the listening position and the sound radiated by the loudspeaker via a secondary path, and generating corresponding array microphone signals. It further includes controlling noise by receiving a noise signal representative of noise generated by the noise source and filtering the noise signal with a controllable noise reduction transfer function to generate the sound signal supplied to the loudspeaker. Controlling noise further includes controlling the noise reduction transfer function based on the noise signal and a virtual error signal, and generating the virtual error signal based on the error signal and the noise signal filtered with a Green's function matrix, the Green's function matrix being configured to be controlled dependent on the array signals.