Composite Ear Tip Structure for High-Frequency Noise Attenuation
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Solution Overview
Problem
Modern in-ear headphones rely heavily on passive noise attenuation provided by low durometer silicone eartips, which are ineffective at attenuating high frequencies (1 kHz to 1.5 KHz), allowing undesired noise to pass through.
Innovation Solution
The development of ear tips with a combination of materials and designs, including a rigid inner wall with an oblong cross-section to prevent rotation and a high durometer compliant material for improved passive attenuation, along with viscoelastic materials for frequency stiffening and sebum resistance, to enhance noise reduction across various frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low durometer silicone is used for eartips, then comfort and acoustic seal are improved, but high frequency noise attenuation (1 kHz to 1.5 KHz) deteriorates
Solution Approach 1:
The eartip is constructed using composite materials: a soft outer layer (low durometer silicone, 10-30 Shore A) for comfort and sealing, combined with a rigid inner core (high durometer material, 60-80 Shore A) for high-frequency noise attenuation. This composite structure allows the eartip to simultaneously achieve comfort, acoustic seal, and effective high-frequency noise blocking.
Solution Approach 2:
Different regions of the eartip have different material properties optimized for their specific functions. The outer surface uses soft low-durometer material for comfort and sealing against the ear canal, while the inner core uses rigid high-durometer material for noise attenuation. This local differentiation of material quality resolves the contradiction between comfort and noise blocking.
2Ease of operation
If conventional round cross-section eartips are used, then ease of insertion is improved, but rotation control and secure fit deteriorate
Solution Approach 1:
The eartip transitions from a conventional round cross-section to an asymmetric oblong cross-section. This asymmetric shape provides directional insertion guidance (easy to insert in the correct orientation) while preventing rotation once inserted, as the oblong shape does not match the circular opening of the ear canal when rotated. This resolves the contradiction between ease of insertion and rotation control.
3Ease of manufacture
If single-material eartips are used, then manufacturing simplicity is improved, but performance across multiple frequencies deteriorates
Solution Approach 1:
The eartip uses a composite structure with at least two different materials: a soft outer layer (low durometer silicone) for comfort and sealing, and a rigid inner core (high durometer material) for high-frequency noise attenuation. This composite construction enables effective noise attenuation across multiple frequency ranges while maintaining comfort and seal quality.
Solution Approach 2:
The invention changes the durometer parameter of the eartip material from uniform low durometer to a gradient or layered structure with both low and high durometer regions. This parameter differentiation allows the eartip to perform effectively across multiple frequency ranges, with the soft outer layer handling lower frequencies and the rigid inner core handling high frequencies.
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 proposed ear tips provide enhanced passive noise attenuation in the 1 kHz to 1.5 KHz range, ensuring a secure fit and improved acoustic seal, thereby reducing noise transmission effectively.
Implementation Method 1
The outer wall and the extension are formed at least partially of a viscoelastic material with frequency stiffening behavior
Implementation Method 2
The inner wall includes a ring that is formed of a rigid material and engages and conforms to the oblong shape of the nozzle, which inhibits improper mounting of the ear tip on the nozzle and inhibits rotation of the ear tip relative to the nozzle
Implementation Method 3
The inner wall includes a high durometer compliant material that defines at least part of an extension that extends between the nozzle and the first end of the ear tip
Data Source
AI summary
An ear tip includes a body configured to be mounted onto an earbud. The body includes a first end, a second end opposite the first end, and a first wall extending between the first and second ends. The first wall defines and surrounds a hollow passage that is configured to conduct sound waves. The first wall is configured to engage a nozzle on the earbud. The first wall includes a ring that is formed of a rigid material and engages the nozzle. The ring includes at least one C-shaped member with at least one gap and a compliant material is molded around the ring and fills the gap.