In-Ear ANR Earphone Acoustic Coupling for Uniform Noise Cancellation
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Solution Overview
Problem
Existing in-ear active noise reduction earphones face challenges in achieving uniform noise cancellation across different users due to variations in ear anatomy, which compromises sound cancellation performance.
Innovation Solution
The implementation of a feedback microphone system with a digital filter that adjusts based on individual ear anatomy, using a housing and ear tip design with a controlled acoustic impedance to optimize noise cancellation, and a customizable digital filter generated based on specific user responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If acoustic measures (nozzle with specific L/A ratio) are used to achieve uniform response across different users, then response uniformity is improved, but noise cancellation performance is compromised
Solution Approach 1:
The patent applies dynamics by making the acoustic coupling variable rather than fixed. The ear tip is designed to be compressible and adaptable, allowing the acoustic impedance to change dynamically based on insertion depth and user anatomy. This enables the system to maintain optimal noise cancellation performance across different users without compromising response uniformity, as the acoustic coupling adapts to each user's unique ear canal dimensions.
Solution Approach 2:
The patent changes the acoustic impedance parameters of the ear tip to resolve the contradiction. By modifying the ear tip material properties, dimensions, and compressibility characteristics, the system achieves both uniform response and high noise cancellation performance. The ear tip is designed with specific acoustic impedance values that can be adjusted through material selection and geometric parameters to optimize both uniformity and cancellation effectiveness.
2Reliability
If the acoustic coupling is optimized for high noise cancellation, then noise cancellation performance is improved, but response variation between different users increases
Solution Approach 1:
The patent employs feedback mechanisms where the system measures the actual acoustic response in the user's ear and adjusts the noise cancellation algorithm accordingly. The earphone includes sensors that detect the acoustic environment and provide feedback to the control circuit, which then modifies the anti-noise signal generation to compensate for individual anatomical variations. This feedback loop enables high noise cancellation performance while maintaining response uniformity across different users.
Solution Approach 2:
The patent applies preliminary action through an initialization phase where the system characterizes the user's ear canal acoustics before full noise cancellation operation begins. During this preliminary phase, the system measures the transfer function and acoustic impedance of the specific user's ear, then pre-configures the noise cancellation parameters optimized for that user's anatomy. This preliminary characterization enables subsequent high-performance noise cancellation while accounting for individual variations.
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 provides improved noise reduction by combining a variable physical design with customized filters, achieving better noise cancellation performance tailored to each user's ears while minimizing ear-to-ear variation.
Implementation Method 1
a feedback microphone for detecting noise
Implementation Method 2
an electroacoustic driver for transducing the antinoise signal into acoustic energy
Implementation Method 3
The acoustic coupling includes a tube of air defined by the combination of the housing and ear tip, having a length L and effective cross-sectional area A such that the ratio L/A is less than 0.6 mm−1
Data Source
AI summary
An active noise reduction (ANR) earphone system includes a feedback microphone for detecting noise, feedback circuitry, responsive to the feedback microphone, for applying a digital filter Kfb to an output of the feedback microphone to produce an antinoise signal, an electroacoustic driver for transducing the antinoise signal into acoustic energy, a housing supporting the feedback microphone and the driver near the entrance to the ear canal, and an ear tip for coupling the housing to the external anatomical structures of a first ear of a user and positioning the housing to provide a consistent acoustic coupling of the feedback microphone and the driver to the ear canal of the first ear. The acoustic coupling includes a tube of air defined by the combination of the housing and ear tip, having a length L and effective cross-sectional area A such that the ratio L/A is less than 0.6 m−1.