Headphone Wind Noise Detection and Occlusion Mitigation
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Solution Overview
Problem
Headphones muffle external sounds and suffer from an occlusion effect, where internal sounds are over-emphasized, and wind noise is amplified, especially in low frequencies, due to passive attenuation and bone conduction, affecting the user's experience.
Innovation Solution
An audio processing system with a digital audio processor in the headphone housing that uses an external microphone and an accelerometer to detect wind noise, applying a feedforward filter to reduce low-frequency gain relative to high frequencies and a feedback filter to mitigate the occlusion effect, combining signals to produce sound with transparency and reduced wind noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If headphones use passive attenuation to block external sounds, then noise isolation is improved, but wind noise in low frequencies is amplified
Solution Approach 1:
The system uses a feedback loop where the external microphone captures wind noise, the audio processor analyzes it, and adjusts the feedforward filter coefficients in real-time to cancel out the amplified wind noise while preserving the noise isolation benefit
Solution Approach 2:
The system dynamically changes the parameters of the feedforward filter based on detected wind conditions. When wind noise is detected, the filter coefficients are adjusted to reduce low-frequency gain, thereby preventing wind noise amplification while maintaining passive attenuation for other frequencies
2Object-affected harmful factors
If headphones block the aural canal for noise isolation, then external sound blocking is improved, but the occlusion effect is worsened
Solution Approach 1:
The system introduces an intermediary feedback path using the internal microphone and audio processor. This intermediary captures bone conduction sounds and external sounds separately, processes them, and reconstructs the audio output to cancel the occlusion effect while maintaining noise isolation
Solution Approach 2:
The system replaces the purely mechanical passive attenuation approach with an electronic audio processing system that uses microphones, processors, and filters to achieve noise isolation without the harmful occlusion effect. The electronic system can selectively cancel unwanted frequencies while preserving desired sounds
3Loss of information
If transparency effect is enabled to allow external sounds, then environmental awareness is improved, but wind noise is amplified
Solution Approach 1:
The system applies different quality treatments to different frequency components of external sounds. The feedforward filter selectively allows high-frequency environmental sounds to pass through while attenuating low-frequency wind noise, achieving local quality optimization in the frequency domain
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 effectively reduces wind noise and occlusion effects, allowing for faithful reproduction of external sounds without amplifying low-frequency wind noise, enhancing the user's awareness of the surroundings while minimizing internal sound distortion.
Implementation Method 1
an accelerometer within the headphone housing to receive vibration through bone conduction
Implementation Method 2
analyze signals from the internal microphone, the external microphone and the accelerometer
Data Source
AI summary
A headphone has a driver, an internal microphone, an accelerometer, and an external microphone. An audio processor analyzes signals to detect wind noise. Gain of lower frequencies is reduced relative to higher frequencies, in a first filter that is operating on an audio signal from the external microphone in a feedforward path, responsive to detecting increased wind noise. A second filter in an audio signal feedback path may be adjusted to compensate for the gain change in the first filter that may mitigate occlusion effect. Outputs of the feedforward path in the feedback path are combined to produce an audio signal for the driver. The driver produces sound in the aural canal that has transparency with reduced wind noise, relative to sound external to the headphone. Other aspects are also described and claimed.