Multipath Audio Compression for Bone- and Air-Conduction Headphones
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Solution Overview
Problem
Bone-conduction headphones are ineffective for high-frequency sounds and cause tactile sensations due to direct contact with the head, limiting their usability for ordinary consumers.
Innovation Solution
An apparatus combining air-conduction and bone-conduction transducers, with filters and audio processing techniques to separate and process audio signals into different frequency ranges, reducing dynamic range through compression to balance loudness perception and minimize tactile sensations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bone-conduction transducers are used to transmit sound through direct contact with the head, then sound transmission is achieved, but tactile sensations and tickling occur at high intensity
Solution Approach 1:
The audio signal is segmented into different frequency components, with low-frequency signals directed to the bone-conduction transducer and high-frequency signals directed to the air-conduction transducer. This segmentation allows the bone-conduction path to operate only at intensities that avoid tactile sensations while maintaining sound transmission effectiveness.
Solution Approach 2:
Different transducers are assigned to different frequency ranges based on their suitability for those ranges. The bone-conduction transducer handles low frequencies where it is effective, while the air-conduction transducer handles high frequencies where bone conduction is ineffective, optimizing overall performance while minimizing tactile sensations.
2Adaptability or versatility
If bone-conduction headphones are used, then external sound can be heard simultaneously, but high-frequency sound transmission is ineffective
Solution Approach 1:
The system merges bone-conduction and air-conduction transducers into a single headphone device, allowing both transmission paths to operate simultaneously. The bone-conduction path provides low-frequency sound and external sound awareness, while the air-conduction path supplements high-frequency sound transmission, achieving full-frequency coverage with maintained environmental awareness.
3Reliability
If audio signals are separated into frequency ranges, then appropriate transducers can be used for each range, but device complexity increases
Solution Approach 1:
An audio compressor serves as an intermediary device that automatically separates the audio signal into different frequency ranges and directs them to appropriate transducers. This mediator handles the complex signal processing tasks, reducing the burden on the main processor and simplifying the overall system architecture while maintaining frequency-specific optimization.
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
Enhances audio delivery by effectively transmitting high-frequency sounds through air-conduction and low-frequency sounds through bone-conduction, reducing tickling sensations and improving overall listening comfort.
Implementation Method 1
The air-conduction transducer may be configured to convert a component of the audio signals to air vibrations detectable by an ear of the user
Implementation Method 2
The bone-conduction transducer may be configured to convert another component of the audio signals to vibrations in a cranial bone of the user via direct contact with the user
Implementation Method 3
compressors may be used to reduce the output intensity of the components relative to the input intensity
Data Source
AI summary
An apparatus for delivering audio signals to a user includes an air-conduction transducer and a bone-conduction transducer. The air-conduction transducer is configured to convert a component of the audio signals to air vibrations detectable by an ear of the user. The bone-conduction transducer is configured to convert another component of the audio signals to vibrations in a cranial bone of the user via direct contact with the user. The apparatus employs one or more filters to separate input audio signals to produce a high-frequency component, a mid-frequency component, and a low-frequency component. The mid- and low-frequency components are processed using compressors to reduce the dynamic range of the components, and then combined to produce a combined component. The combined component is delivered to the user through the bone-conduction transducer, and the high-frequency component is delivered to the user through the air-conduction transducer.