Active Noise Control Phase Correction for Road Noise
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Solution Overview
Problem
Existing active noise control techniques for vehicle interiors face challenges in effectively reducing random noise like road noise, as feedforward methods require a reference signal with low correlation and causality issues, while feedback methods in closed-type devices cause oppressive feelings and block external sound.
Innovation Solution
A non-closed-type active noise control device employing feedback control with a noise detection unit, a correction unit that delays the phase of detected noise signals in the low frequency band, and an output unit to reduce noise based on the corrected signal, using a low boost filter to enhance gain and correct phase in the low frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If feedforward control is used to reduce random noise, then the device structure is simple, but the noise reduction effect is insufficient due to low correlation between reference signal and random noise
Solution Approach 1:
The patent employs feedback control where the noise detection unit continuously monitors the actual noise level and the correction unit adjusts the noise reduction signal accordingly. This closed-loop feedback mechanism enables the system to adapt to varying noise conditions and maintain effective noise reduction without requiring complex reference signals, thus resolving the contradiction between structural simplicity and noise reduction effectiveness.
2Reliability
If closed-type feedback control is used to reduce random noise, then the noise reduction effect is high, but the user experiences oppressive feelings and cannot hear external sound
Solution Approach 1:
The patent applies local quality by selectively applying noise reduction only in the low frequency band where road noise predominates, while leaving high frequency sounds relatively unaffected. The correction unit processes only the low frequency component of the noise signal, allowing the user to maintain awareness of external high frequency sounds while benefiting from noise reduction in the problematic low frequency range, thus improving user comfort without sacrificing noise reduction effectiveness.
3Ease of operation
If feedback control without phase correction is used in non-closed structure, then the device is open-type and comfortable for users, but the noise reduction effect deteriorates in the low frequency band
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the phase of the noise signal in the low frequency band through the correction unit. The correction unit introduces a phase delay to the low frequency component of the noise signal, which optimizes the noise reduction effectiveness. This parameter adjustment enables the open-type device to achieve both user comfort and effective low frequency noise reduction simultaneously.
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 solution effectively reduces random noise like road noise without the need for a reference signal, allowing for open-type usage in vehicles while maintaining noise reduction efficacy across a broader frequency band, ensuring user comfort and external sound accessibility.
Implementation Method 1
a correction unit configured to delay a phase of a detected noise signal in a low frequency band
Implementation Method 2
an output unit configured to output a noise reduction sound which reduces the noise based on the corrected noise signal
Data Source
AI summary
The active noise control device detects noise, and delays a phase of a detected noise signal in a low frequency band. In a non-closed-type noise control device, since there occurs such a phenomenon that the phase of the noise signal advances in the low frequency band, the correction unit performs a correction to cancel the phase advance by delaying the phase. By outputting the noise reduction sound based on the phase-corrected noise signal, the noise is reduced.