Adaptive Noise Control Gain Scaling Circuit
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Solution Overview
Problem
Adaptive noise cancellation systems in personal audio devices, such as wireless telephones, lack the ability to effectively reduce the noise cancellation effect as users desire, as the adaptive systems compensate for reduced anti-noise gain, leading to a return to the original ANC effect.
Innovation Solution
An integrated circuit with a processing circuit that includes an adaptive filter, a scaling portion, a coefficient control block, and a biasing portion, which generates and scales an anti-noise signal to minimize ambient audio sounds, allowing for independent adjustment of the adaptive filter's response to control the ANC effect, enabling users to selectively reduce the noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the gain of the anti-noise signal is reduced in an adaptive noise cancellation system, then the ANC effect is weakened, but the adaptive system compensates by adapting further to restore the original ANC effect
Solution Approach 1:
The patent introduces a dynamic control mechanism where the adaptive filter's response is independently adjusted through a biasing portion that modifies the coefficient update process. This allows the system to maintain stable ANC effects while enabling user control through the scaling portion, resolving the contradiction between ease of operation and reliability by making the adaptation process dynamically controllable rather than purely automatic
Solution Approach 2:
The patent employs a feedback mechanism where the biasing portion continuously monitors and adjusts the adaptive filter's response based on the scaling factor applied to the anti-noise signal. This feedback loop prevents the adaptive system from completely compensating for user-desired reductions in ANC effect, thereby maintaining reliability while respecting user control preferences
2Adaptability or versatility
If a fixed feedback filter or fixed feedforward filter is used, then reducing the ANC effect is easily accomplished by reducing gain, but the system lacks adaptability to environmental changes
Solution Approach 1:
The patent segments the noise cancellation system into distinct functional portions: an adaptive filter for environmental adaptation, a scaling portion for user control, and a biasing portion to maintain stability. This segmentation allows the system to simultaneously achieve adaptability through the adaptive filter and user control through the scaling portion, resolving the contradiction between adaptability and ease of operation
Solution Approach 2:
The biasing portion acts as an intermediary between the adaptive filter and the scaling portion, mediating the interaction between automatic adaptation and user control. It ensures that the adaptive system's response is shaped in conformity with both the reference microphone signal and error microphone signal while respecting the scaling factor applied by the user, thereby enabling both adaptability and user control
Data Source
AI summary
A method may include adaptively generating an anti-noise signal for countering the effects of ambient audio sounds at an acoustic output of the transducer by adapting a response of an adaptive filter that filters a reference microphone signal in conformity with an error microphone signal and the reference microphone signal to minimize the ambient audio sounds in the error microphone, generating a scaled anti-noise signal by applying a scaling factor to the anti-noise signal, further adjusting the response of the adaptive filter independent of a source audio signal by altering an input to the coefficient control block of the adaptive filter to compensate for the scaling factor, and combining the scaled anti-noise signal with the source audio signal to generate an audio signal provided to the transducer.