Adaptive Noise Control With Adjustable Gain Factors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing active noise control systems face challenges in maintaining effective noise cancellation performance due to variations in the secondary path transmission function, affecting the speed and quality of adaptation, and lack the ability to selectively control cancellation characteristics over frequency and phase.
Innovation Solution
An adaptive noise control system that includes an adaptive filter and a signal processing arrangement to generate compensation signals with adjustable gain factors, allowing for real-time adjustment of the secondary path estimation and selective noise attenuation characteristics, enabling improved noise reduction and phase control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the secondary path transmission function is used for noise cancellation, then noise reduction is achieved, but variations in the transmission function affect the speed and quality of adaptation
Solution Approach 1:
The patent implements dynamic adaptation by continuously updating the secondary path transmission function estimate based on incoming error signals and reference signals. The adaptive filter coefficients are adjusted in real-time to track variations in the secondary path, allowing the system to maintain effective noise cancellation despite changes in acoustic conditions. This dynamic updating mechanism enables the system to adapt to varying transmission characteristics without manual intervention.
Solution Approach 2:
The system employs feedback through the error signal (microphone output) to continuously monitor the actual noise cancellation performance. This error signal is fed back to the adaptive filter to adjust the compensation signal generation. The feedback loop enables the system to detect deviations from optimal performance caused by secondary path variations and automatically correct them, maintaining reliable noise cancellation while adapting to changing conditions.
2Reliability
If conventional adaptive noise control is used, then noise cancellation is achieved, but the system lacks selective control over cancellation characteristics
Solution Approach 1:
The patent applies local quality by implementing frequency-dependent gain factors that allow different cancellation characteristics at different frequency bands. Instead of uniform noise cancellation across all frequencies, the system can apply selective attenuation gains to specific frequency ranges, enabling tailored noise control that preserves desirable acoustic characteristics while eliminating unwanted noise. This allows selective control over which frequency components are cancelled and which are preserved.
Solution Approach 2:
The system enables parameter changes by allowing dynamic adjustment of attenuation gains and phase characteristics through the signal processing arrangement. Users can modify the transfer function parameters to achieve desired cancellation characteristics, such as adjusting the strength of cancellation at different frequencies or changing the phase relationship between noise and compensation signals. This provides flexible control over the cancellation behavior to match different application requirements.
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 achieves enhanced noise reduction performance by adapting to variations in the secondary path and allowing for user-selectable attenuation and phase adjustments, thereby improving the speed and quality of noise cancellation.
Implementation Method 1
at least one acoustic transducer that receives the first electrical compensation signal and radiates an acoustic compensation signal indicative of the first electrical compensation signal to the listening position
Implementation Method 2
a disturbing noise... is sound that is not intended to be heard or perceived... noise control systems and methods are known that eliminate or at least reduce the noise radiated into a listening room using a destructive interference
Data Source
AI summary
Adaptive noise control for reducing power of an acoustic noise signal radiated from a noise source to a listening position comprises providing an electrical reference signal correlated with the acoustic noise signal; filtering the electrical reference signal with an adaptive filter to provide an electrical output signal; multiplying the electrical output signal of the adaptive filter by a gain factor to provide a first electrical compensation signal; filtering and multiplying the electrical output signal of the adaptive filter by the inverse of the gain factor to provide a second electrical compensation signal, the second gain factor being equal to 1 subtracted by the first gain factor; radiating the first electrical compensation signal to the listening position with an acoustic transducer; sensing a residual electrical error signal at the listening position; adding the second electrical compensation signal to the electrical error signal to provide a compensated error signal; and adapting filter coefficients of the adaptive filter as a function of the compensated error signal and the reference signal.