Adaptive Active Noise Control Signal Level Adjustment
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Solution Overview
Problem
Conventional active noise control systems can produce abnormal sounds when noise levels decrease, as the cancel sound may become louder than the noise it is intended to cancel, leading to ineffective noise reduction.
Innovation Solution
An active noise control device with a level detection unit that adjusts the cancel signal based on the detected signal level of the reference signal, ensuring the cancel sound is not excessively loud by decreasing its amplitude when the noise level is low, thereby preventing abnormal sounds and maintaining effective noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cancel sound is generated to effectively reduce noise, then the noise reduction effect is improved, but when noise level decreases, the cancel sound becomes louder than the noise and creates abnormal sounds
Solution Approach 1:
The patent applies dynamics by making the cancel signal generation adaptive to changing noise conditions. The level detection unit continuously monitors the reference signal level, and the control block dynamically adjusts the cancel signal generation based on detected noise levels. This allows the system to transition from a static cancel signal approach to a dynamic one that adapts to varying noise environments, preventing abnormal sounds when noise levels decrease while maintaining effective noise reduction when noise levels are high.
Solution Approach 2:
The patent implements feedback by introducing a level detection unit that monitors the reference signal and feeds this information back to the control block. The control block uses this feedback to adjust the cancel signal generation appropriately. This closed-loop feedback mechanism ensures that the cancel sound level is continuously adjusted based on the actual noise level, preventing the cancel sound from becoming louder than the noise it intends to cancel.
2Reliability
If the cancel signal level is increased to match high noise levels, then noise reduction effectiveness is improved, but the system becomes unable to adapt when noise levels decrease
Solution Approach 1:
The system transitions from a fixed cancel signal level to a dynamic one that adapts to varying noise conditions. The level detection unit continuously monitors noise levels, and the control block adjusts the cancel signal generation in real-time based on these variations, enabling the system to maintain effectiveness across different noise environments.
Solution Approach 2:
The patent changes the parameter of cancel signal level dynamically based on the detected reference signal level. When noise levels are high, the cancel signal level is increased to maintain effective noise reduction. When noise levels decrease, the cancel signal level is reduced accordingly. This parameter adjustment ensures both noise reduction effectiveness and adaptability to varying noise conditions.
3Reliability
If the cancel sound is continuously generated at a high level, then effective noise cancellation is achieved, but energy consumption increases and abnormal sounds occur during low noise periods
Solution Approach 1:
The patent implements periodic monitoring of the reference signal level through the level detection unit, which continuously detects noise levels and triggers appropriate cancel signal generation only when needed. This periodic detection and conditional response approach ensures that energy is consumed only during high noise periods when noise cancellation is actually required, rather than continuous high-level cancel sound generation.
Solution Approach 2:
The system dynamically changes the cancel signal level parameter based on detected noise conditions. During high noise periods, the cancel signal is generated at a higher level for effective noise cancellation. During low noise periods, the cancel signal level is reduced or stopped, thereby reducing energy consumption while maintaining noise cancellation effectiveness when needed.
Data Source
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AI summary
In an active noise control device, in order to solve this problem, a control block determines a level of a reference signal detected by a level detection unit. If determining that the level of the reference signal is small, the control block decreases a level of a cancel signal. This operation suppresses generation of an abnormal sound even if a level of a noise is small.