In-Ear ANC Earphone Acoustic Volume Stabilization
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Solution Overview
Problem
In-ear active noise-cancelling (ANC) earphones experience quality reduction due to leaks, varying ear canal geometries affecting transducer loads, and instability when operated in open sound fields, leading to bass drops and acoustic overmodulation.
Innovation Solution
The acoustic channel and speaker are positioned adjacent to each other at the ear tip, with a connecting acoustic channel routed to an additional volume, reducing the impact of varying ear canal geometries and stabilizing the ANC circuit by increasing the frontal volume and incorporating the microphone in the additional volume for improved mechanical robustness and low-pass characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the earphone is designed for closed-volume operation in the ear canal, then ANC performance is optimized, but the earphone produces bass drops and instability when operated in open sound fields
Solution Approach 1:
The earphone is designed with dual acoustic pathways: a sealed pathway for closed-volume operation and an open pathway through the second acoustic channel leading to the environment. This allows the device to function effectively in both closed and open sound fields, eliminating the trade-off between ANC performance and open-field adaptability
Solution Approach 2:
A second acoustic channel acts as an intermediary pathway that connects the ear canal to the environment independently of the sealed acoustic chamber. This intermediary channel provides environmental reference sound to the ANC system while maintaining the sealed chamber's acoustic integrity, enabling stable operation in both closed and open conditions
2Reliability
If the acoustic channel and speaker are positioned separately to reduce leakage impact, then bass drop is reduced, but the device complexity increases
Solution Approach 1:
The speaker and acoustic channel are positioned adjacently and integrated into a unified acoustic assembly within the earphone housing. This merging of components reduces the impact of leaks while maintaining a compact design that does not significantly increase overall device complexity
Solution Approach 2:
The acoustic system is segmented into distinct functional pathways: a primary sealed acoustic channel for bass response and a secondary open acoustic channel for environmental reference. This segmentation allows independent optimization of each pathway's function while managing overall system complexity
3Reliability
If the frontal volume is increased to stabilize the ANC system, then the critical frequency is reduced and ANC stability improves, but the available space in the ear canal is exceeded
Solution Approach 1:
The acoustic volume is extended along the longitudinal dimension of the ear canal rather than expanding radially. The second acoustic channel extends forward from the speaker assembly, effectively increasing the frontal volume in the direction of sound propagation while maintaining a compact transverse profile that fits within the ear canal
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 configuration linearizes the secondary path, stabilizes the ANC system under varying wearing conditions, reduces bass drops, and suppresses high-frequency instability, providing enhanced operational stability and sound quality.
Implementation Method 1
the acoustic channel of the speaker, possibly the speaker itself as well, and a connecting acoustic channel (tube) are positioned adjacent to each other in the tip part
Implementation Method 2
an additional volume preferably arranged at a distance from the output in the vicinity of the speaker and possibly around the speaker
Data Source
AI summary
In-ear active noise-cancelling (ANC) earphones for which the ANC circuit remains stable even under varying wearing conditions, the earphones being worn so that an eartip of the earphone is at least partially in the external auditory canal, with at least one speaker with a frontal volume leading to a tip area and/or speaker channel, and with at least one ANC microphone. To ensure that the ANC circuit remains stable even with a small available space, the earphones feature the connection of a frontal volume and/or a speaker channel with an additional volume via a tube ending in the tip area.