Active Noise Reduction Speaker Switching to Prevent Amplifier Clipping
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Solution Overview
Problem
Conventional noise cancellation systems fail to effectively match the spatially flat noise field with a uniform sound pressure field, leading to inefficient noise cancellation and audible artifacts when the occupant turns their head, and can result in amplifier clipping during certain noise events.
Innovation Solution
The system employs an arrayed speaker configuration to produce a substantially uniform sound pressure field that matches the noise field in magnitude and phase, and transitions to an in-phase configuration during high-output noise events to avoid clipping, using a signal director module to dynamically adjust the proportion of the command signal between the arrayed and in-phase speaker controllers based on voltage magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an arrayed speaker configuration is used to produce a uniform sound pressure field, then noise cancellation effectiveness is improved, but amplifier output voltage increases causing clipping during high noise events
Solution Approach 1:
The system dynamically switches between arrayed and in-phase speaker configurations based on real-time noise levels. During normal conditions, the arrayed configuration provides effective noise cancellation. When high noise events are detected, the system transitions to the in-phase configuration to reduce amplifier output voltage and avoid clipping, thus adapting to changing conditions and resolving the contradiction between cancellation effectiveness and amplifier saturation.
2Object-generated harmful factors
If an in-phase speaker configuration is used to reduce amplifier output voltage, then amplifier clipping is avoided, but noise cancellation effectiveness decreases
Solution Approach 1:
The system uses dynamic switching to select the appropriate speaker configuration based on real-time conditions. The in-phase configuration is activated only during high noise events to prevent amplifier clipping, while the arrayed configuration is used during normal conditions to maximize noise cancellation effectiveness. This dynamic adaptation allows the system to optimize performance for each specific situation.
Solution Approach 2:
The system changes the operational parameters of the speaker system by switching between arrayed and in-phase configurations. This parameter change involves modifying the phase relationships and signal distribution to the speakers, allowing the system to operate at different performance characteristics depending on the noise environment, thus avoiding amplifier clipping while maintaining cancellation effectiveness when needed.
3Stability of the object's composition
If the speaker configuration is fixed in arrayed mode, then uniform sound pressure field is maintained, but the system cannot adapt to high noise events causing amplifier saturation
Solution Approach 1:
The system transitions from a static, fixed configuration to a dynamic, adaptable configuration. The speaker system can switch between arrayed and in-phase modes based on real-time noise level detection, allowing it to adapt to varying environmental conditions while maintaining the ability to produce uniform sound pressure fields during normal operation.
Solution Approach 2:
The system changes its operational parameters by switching between different speaker configurations. This allows the system to adapt to high noise events by changing from arrayed mode (for uniform field production) to in-phase mode (for reduced voltage output), thereby gaining versatility without sacrificing the stability of uniform sound pressure field generation under normal conditions.
4Object-generated harmful factors
If the speaker configuration is fixed in in-phase mode, then amplifier clipping is avoided, but uniform sound pressure field production is lost
Solution Approach 1:
The system dynamically switches between arrayed and in-phase configurations based on real-time noise levels. During normal conditions, the arrayed configuration produces a uniform sound pressure field. When high noise events are detected, the system transitions to the in-phase configuration to reduce amplifier output voltage and avoid clipping, thus adapting to changing conditions and resolving the contradiction between cancellation effectiveness and amplifier saturation.
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 increases the noise cancellation zone around the head of the occupant, reduces audible artifacts, and prevents amplifier clipping by efficiently managing speaker output during noise-related events, maintaining effective noise cancellation while minimizing inefficiencies.
Implementation Method 1
producing, by the arrayed speaker controller, a driver signal for each of the speakers in response to the command signal such that combined sound emitted by the speakers in response to the driver signals produces a substantially uniform sound pressure field having a magnitude and phase adapted to attenuate a noise field
Implementation Method 2
producing, by the in-phase speaker controller, a common in-phase driver signal for all of the speakers in response to the command signal
Data Source
AI summary
A noise cancellation method and system comprises a system controller that produces a command signal in response to a signal from at least one microphone detecting sound in an area. The system controller includes an arrayed speaker controller for producing a driver signal for each speaker in response to the command signal such that combined sound emitted by the speakers in response to the driver signals produces a substantially uniform sound pressure field adapted to attenuate a noise field corresponding to the sound detected by the at least one microphone. The system controller includes an in-phase speaker controller for producing a common in-phase driver signal for all speakers in response to the command signal and a signal director module for proportioning the command signal between the arrayed and in-phase speaker controllers in response to a magnitude of voltage associated with driving the speakers in accordance with the command signal.