Cartilage Conduction Audio for Eyewear
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Solution Overview
Problem
Existing audio systems in head-mounted displays for virtual, augmented, and mixed reality often obstruct the ear canal, limiting immersive and safe experiences by covering the ear, and struggle to provide full-frequency audio while keeping the ear canal open, leading to issues with crosstalk and power consumption.
Innovation Solution
A cartilage conduction audio system that uses a transducer assembly behind the ear to vibrate the auricle, creating acoustic pressure waves, while an acoustic sensor detects these waves to adjust the frequency response, ensuring the ear canal remains open and providing individualized audio experiences with reduced crosstalk and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional speakers or personal audio devices are used to provide sound to users, then audio functionality is achieved, but the ear canal is obstructed and covered, limiting immersive and safe experiences
Solution Approach 1:
The audio system is segmented into two independent pathways: traditional air conduction through the ear canal and cartilage conduction through the auricle. This segmentation allows the ear canal to remain open for spatial awareness while the cartilage conduction pathway provides audio output, resolving the contradiction between ear canal openness and audio functionality.
Solution Approach 2:
The cartilage of the auricle serves as an intermediary medium to transmit vibrations from the transducer to the skull bones, which then conduct sound to the inner ear. This intermediary pathway enables audio delivery without requiring ear canal obstruction, maintaining both ear canal openness and audio experience quality.
2Reliability
If the ear canal is kept open for spatial awareness, then immersive and safe experience is improved, but traditional audio delivery methods cannot function
Solution Approach 1:
The acoustic field transmission method is replaced with mechanical vibration transmission. Instead of using air pressure waves through the ear canal, the system uses mechanical vibrations applied to the cartilage and skull bones to deliver audio, enabling audio delivery while keeping the ear canal open for spatial awareness.
3Reliability
If a full frequency audio reproduction system is implemented on an eyewear device, then audio quality is improved, but the device becomes heavier and more complex
Solution Approach 1:
The audio transmission function is extracted from the traditional ear canal pathway and relocated to the cartilage conduction pathway. This extraction allows for a simplified transducer design that can be integrated into lightweight eyewear, achieving full frequency audio reproduction without the weight and complexity of traditional headphone systems.
4Reliability
If traditional headphones are used to provide audio, then audio output is achieved, but power consumption increases and crosstalk occurs between ears
Solution Approach 1:
The system uses mechanical vibration of the cartilage and skull bones to directly transmit audio signals to the inner ear, bypassing the need for high-power acoustic amplification through the ear canal. This mechanical vibration approach reduces power consumption while maintaining audio output quality and eliminates crosstalk between ears through direct bone conduction pathways.
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 system enhances user experience by maintaining an open ear canal for immersive and safe audio, reducing crosstalk and power consumption, and improving ergonomics through cartilage conduction, providing a comfortable and efficient audio solution for wearable devices.
Implementation Method 1
The transducer assembly is coupled to a back of an auricle of the user to vibrate the auricle over a frequency range, creating an acoustic pressure wave
Implementation Method 2
The transducer assembly includes a piezoelectric transducer to generate vibrations over a first portion of a frequency range
Implementation Method 3
a moving coil transducer to generate vibrations over a second portion of the frequency range
Implementation Method 4
The acoustic sensor detects the acoustic pressure wave at an entrance of the ear of the user
Data Source
AI summary
An audio system includes a transducer assembly, an audio sensor, and a controller. The transducer assembly is coupled to a back of an auricle of an ear of the user. The transducer assembly vibrates the auricle over a frequency range to cause the auricle to create an acoustic pressure wave in accordance with vibration instructions. The acoustic sensor detects the acoustic pressure wave at an entrance of the ear of the user. The controller dynamically adjusts a frequency response model based in part on the detected acoustic pressure wave, updates the vibration instructions using the adjusted frequency response model, and provides the updated vibration instructions to the transducer assembly.