Planar Magnetic ANC Headphones With Low-Distortion Feedback
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Solution Overview
Problem
Existing active noise control (ANC) technologies in headphones and earphones, particularly those using cone-and-dome dynamic transducers, suffer from non-linearities and distortion, which are exacerbated by the time delay between the diaphragm and feedback microphone, leading to suboptimal noise cancellation and potential sound quality degradation, especially in high-end audiophile applications where ANC is generally discouraged due to perceived distortion and muffled tones.
Innovation Solution
The implementation of planar magnetic transducers with improved magnetic configurations, multiple diaphragms, and anti-diffraction designs, combined with innovative microphone placement strategies such as embedding microphones on the diaphragm to minimize time delay, and the use of phase plugs for enhanced acoustic loading and phase coherence, enables effective ANC while maintaining high sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If active noise control is implemented using conventional dynamic transducers, then noise cancellation capability is improved, but sound quality deteriorates due to distortion and non-linearities
Solution Approach 1:
The patent changes the fundamental operating parameters of the transducer by using planar magnetic technology instead of conventional dynamic transducers. This involves changing the force generation mechanism from electromagnetic coil interaction to magnetic field interaction with a planar diaphragm, resulting in highly linear operation and reduced distortion while maintaining noise cancellation effectiveness
Solution Approach 2:
The patent replaces the mechanical suspension and voice coil system of dynamic transducers with a planar magnetic system that uses a rigid planar diaphragm and distributed magnetic field. This substitution eliminates the mechanical non-linearities associated with cone/dome suspension systems while preserving the ability to generate controlled acoustic output for noise cancellation
2Manufacturing precision
If planar transducers are used with ANC, then linearity and frequency response are improved, but device complexity increases due to multiple diaphragms and magnet configurations
Solution Approach 1:
The patent divides the planar transducer into multiple independent diaphragms, each capable of being controlled separately. This segmentation allows each diaphragm to be optimized for specific frequency ranges or functions (audio reproduction vs. noise cancellation), simplifying the control algorithm while maintaining high linearity and reducing the need for complex mechanical structures
Solution Approach 2:
The patent designs the planar transducer system to perform multiple functions simultaneously: audio signal reproduction, active noise cancellation, and adaptive noise control. The same planar diaphragm structure serves all three functions by receiving different control signals, eliminating the need for separate transducer systems and reducing overall device complexity
3Object-affected harmful factors
If feedforward ANC with external microphones is used, then noise cancellation is improved, but feedback stability deteriorates due to time delay and phase issues
Solution Approach 1:
The patent introduces an internal reference microphone positioned within the earcup or headphone housing as an intermediary element. This microphone captures the noise signal at the same location where the anti-noise signal will be generated, eliminating time delay and phase mismatch issues between external microphones and the transducer, thereby stabilizing the feedback loop while maintaining effective noise cancellation
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 significantly reduces ANC-related distortion, improves frequency response, and enhances noise cancellation performance, making ANC suitable for high-end audio applications by providing clear and detailed sound reproduction while effectively reducing background noise.
Implementation Method 1
planar magnetic transducers
Implementation Method 2
Active Noise Control (ANC) includes Active Noise Cancellation
Data Source
AI summary
Active noise control (ANC), including active and adaptive noise cancellation (ANC) with non-voice-coil transducers having highly linear transfer functions, such as planar transducers, planar magnetic transducers, electro-static transducers, and piezo-electric transducers. This active and adaptive noise cancellation (ANC) may be used with: planar transducer headphones and earphones; open-backed and closed-back headphones and earphones; in-ear earphones, and phase plugs.