Active Noise Control Headphones with Dynamic Filter Segmentation
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Solution Overview
Problem
Conventional active noise control (ANC) headphones suffer from volume reduction and audio quality loss due to the impact of noise cancellation on audio signals, and are vulnerable to low-frequency noise with high amplitude.
Innovation Solution
The ANC headphones incorporate a speaker, internal microphone, and processor with a filter function module that dynamically adjusts parameters based on system parameters and pre-tested data to minimize the impact of noise cancellation on audio signals, using both feedback and feed forward loops to generate noise-controlled audio signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional ANC is applied to reduce noise, then noise cancellation effect is improved, but audio quality deteriorates due to volume reduction and signal impact
Solution Approach 1:
The patent segments the audio signal processing into multiple independent filter functions: echo cancellation filter, noise reduction filter, and equalization filter. Each filter operates on specific aspects of the signal independently, allowing noise cancellation to be achieved without compromising overall audio quality. The echo cancellation filter removes feedback signals, the noise reduction filter targets specific noise frequencies, and the equalization filter compensates for any audio quality degradation, thereby resolving the contradiction between noise cancellation effectiveness and audio quality preservation.
Solution Approach 2:
The patent dynamically adjusts filter parameters based on real-time system conditions and pre-tested data. The processor determines current system parameters and uses them to optimize filter function parameters, enabling the system to adaptively balance noise cancellation performance with audio quality. This parameter optimization approach allows the ANC system to maintain high audio quality while effectively reducing noise, resolving the technical contradiction between these two competing requirements.
2Object-affected harmful factors
If conventional ANC processes low-frequency noise, then noise cancellation is attempted, but system performance deteriorates due to saturation from high amplitude low-frequency noise
Solution Approach 1:
The patent applies local quality by designing the filter function module to treat different frequency ranges with specialized processing. The noise reduction filter specifically targets low-frequency noise components with appropriate filtering characteristics, while other frequency ranges are processed differently. This localized approach allows effective low-frequency noise reduction without causing system saturation, as each frequency band is optimized independently for its specific characteristics.
Solution Approach 2:
The patent applies partial action by selectively processing only the problematic low-frequency noise components rather than attempting to cancel all frequencies uniformly. The filter function module identifies and processes specific low-frequency noise signals that cause saturation, while leaving other frequencies unaffected. This selective partial processing approach resolves the contradiction by addressing only the harmful low-frequency components without over-processing that would lead to system saturation and instability.
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
This approach effectively reduces the impact of noise cancellation on audio signals, improving user experience by maintaining audio quality and addressing low-frequency noise issues, while allowing for natural and clear sound transmission of external noises.
Implementation Method 1
Headphones can include a pair of small loudspeaker drivers worn on or around the head over a user's ears, which convert an electrical signal to a corresponding acoustic signal
Implementation Method 2
The internal microphone is configured to obtain a mixed audio signal comprising a noise signal and a second audio source signal based on the audio of interest played by the speaker
Implementation Method 3
Active noise control (ANC), also known as noise cancellation, or active noise reduction (ANR), is a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first sound
Data Source
AI summary
Embodiments of active noise control (ANC) headphones and operating methods thereof are disclosed herein. In one example, a headphone includes a speaker, an internal microphone, and a processor. The speaker is configured to play an audio of interest based on an audio source signal. The internal microphone is configured to obtain a mixed audio signal including a noise signal and the audio of interest played by the speaker. The processor is configured to determine a first current system parameter of the headphone based on the mixed audio signal at a first time point, and determine if the first current system parameter of the headphone is higher than a predetermined threshold to determine if the headphone is worn by a user.