In-Ear Speaker HRTF Measurement via Dynamic Head Tracking
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Solution Overview
Problem
Conventional methods for determining head-related transfer functions (HRTFs) are time-consuming and restrictive, requiring subjects to remain still, which limits the scope of binaural sounds that can be synthesized and does not account for changes in position, such as tilting or rotating the head.
Innovation Solution
A system using an in-ear speaker, audio sensors, and image sensors within a soundproof chamber to emit and capture sound waves, allowing for dynamic HRTF measurements by emitting a sine wave sweep and using audio and image sensors to account for body pose changes, enabling a more comprehensive range of binaural sound synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional HRTF measurement methods are used with multiple speakers in a circular arrangement, then measurement precision can be improved by capturing sound from multiple angles, but measurement time increases significantly due to requiring measurements in small angular increments
Solution Approach 1:
The patent replaces the mechanical system of multiple physical speakers arranged in a circular array with a single speaker and electronic signal processing. Instead of physically moving speakers or the subject through angular positions, the system uses a single speaker to emit sounds while electronic processing simulates sounds from multiple angular positions, thereby maintaining measurement precision while dramatically reducing measurement time
Solution Approach 2:
The patent changes the measurement approach from physically varying spatial parameters (speaker positions, subject positions) to varying signal parameters (phase, amplitude, time delays) through electronic processing. By manipulating audio signal parameters rather than physical positions, the system achieves the same HRTF measurement precision much more quickly
2Measurement precision
If the subject is required to remain still during HRTF measurements, then measurement precision is maintained, but the scope of binaural sounds that can be synthesized is limited and the process becomes arduous
Solution Approach 1:
The patent introduces dynamic head tracking that allows the subject to move their head freely during measurements. The system dynamically adjusts the audio signal processing based on real-time head position data from sensors, maintaining measurement precision while enabling the synthesis of binaural sounds for various head orientations and positions, thereby increasing adaptability
Solution Approach 2:
The patent implements feedback through head tracking sensors that continuously monitor subject head position and provide this information to the audio processing system. This feedback loop allows the system to adjust the HRTF calculations in real-time based on actual head movements, maintaining precision while expanding the range of synthesizable binaural sounds to include dynamic head positions
3Device complexity
If conventional HRTF measurement methods are used with fixed speaker positions, then device complexity is reduced, but the system cannot account for changes in subject position such as tilting or rotating the head
Solution Approach 1:
The patent makes the single speaker system universal by combining it with head tracking sensors and dynamic signal processing. This multi-functional approach allows the same hardware configuration to handle both fixed and dynamic measurement scenarios, accommodating various head positions and movements without requiring complex multi-speaker arrangements for each scenario
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 allows for efficient and dynamic HRTF determination, accounting for subject position changes, thereby increasing the scope of binaural sounds that can be synthesized and reducing the time required for measurements.
Implementation Method 1
The in-ear speaker may emit a sound outwardly away from the ear of the subject into the surrounding capture space
Implementation Method 2
An audio reflector coupled to an output end of the audio-transport tube may receive the sound and reflect the sound throughout the capture space
Data Source
AI summary
In one embodiment, a method for emitting a sound from an in-ear speaker worn by a subject includes generating, by an audio source of the in-ear speaker, a source audio signal. One or more speakers of the in-ear speaker may emit a sound based on the audio signal and an audio-transport tube of the in-ear speaker may receive the sound. The one or more speakers may be comprised of a singular speaker or a speaker array coupled to a crossover network. The audio-transport tube has an input end coupled to the one or more speakers to receive the sound. An audio reflector of the in-ear speaker may reflect the sound. The audio reflector is coupled to an output end of the audio-transport tube.