Active Noise Cancellation With Wind-Adaptive Filter Control
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Solution Overview
Problem
Conventional active noise cancellation systems amplify wind noise instead of canceling it due to the random and pressure-based nature of wind, which is not audible but affects the noise microphone, leading to increased wind noise perception.
Innovation Solution
A noise cancellation system with a controllable high pass filter and gain value, where the cut-off frequency and gain are adjusted based on detected wind amplitude using a low pass function and wind noise detection algorithm, specifically using cross-correlation and auto-correlation techniques to differentiate wind noise from ambient noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional active noise cancellation is used in windy conditions, then ambient noise can be cancelled, but wind noise is magnified and becomes more audible
Solution Approach 1:
The system dynamically adjusts the high pass filter cut-off frequency and gain values based on real-time wind detection. When wind is detected, the cut-off frequency is increased and gain is reduced to minimize wind noise amplification. When wind is absent, the filter operates at normal settings for effective ambient noise cancellation. This dynamic adaptation resolves the contradiction by allowing the system to optimize performance for different environmental conditions.
Solution Approach 2:
The invention changes key parameters of the signal processing block - specifically the cut-off frequency of the high pass filter and the gain values - in response to wind conditions. By detecting wind amplitude and using a low pass function to generate control signals, the system modifies these parameters to prevent wind noise from being processed and amplified by the noise cancellation algorithm, thereby eliminating the harmful effect while preserving the beneficial noise cancellation capability.
2Object-generated harmful factors
If wind detection is added to control the noise cancellation system, then wind noise amplification is prevented, but device complexity increases
Solution Approach 1:
The noise microphone serves dual functions: it detects ambient noise for the standard noise cancellation process and simultaneously detects wind conditions through turbulence analysis. The same signal processing block that generates noise cancellation signals also processes wind detection signals. The control block uses the wind detection output to adjust filter parameters, creating a multi-functional system that adds wind control capability without requiring entirely separate detection and control pathways.
Solution Approach 2:
The system implements feedback by using the wind detection signal to continuously adjust the high pass filter cut-off frequency and gain values. The control block receives wind amplitude information and generates control signals that modify the signal processing block's operation in real-time. This closed-loop feedback mechanism allows the system to adapt to changing wind conditions dynamically, providing effective wind noise control through a relatively simple feedback-based approach rather than complex open-loop control systems.
Data Source
AI summary
A noise cancellation system generates a noise cancellation signal from a signal representing ambient noise by signal processing. The signal processing applies a controllable gain value, and includes a high pass filter with a controllable cut-off frequency. A control block detects a wind amplitude. The cut-off frequency of the high pass filter is controlled based on the detected wind amplitude. A low pass function is applied to the detected wind amplitude, and the controllable gain is adjusted based on the output of the low pass function.