Headphone Calibration Using Equalization for Accurate Audio Playback
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Solution Overview
Problem
Existing sound reproduction systems, including stereophonic and binaural systems, fail to accurately recreate the acoustic environment of a live audio event when played back through headphones, due to variables in recording and playback technologies, and headphones used by the listener.
Innovation Solution
A method and apparatus that calibrate user headphones by characterizing the audio colorations caused by reference microphones, a dummy head, and the headphones themselves, using test tones to compute an equalization signal that accounts for the impacts of recording and playback devices, and applies this signal to improve audio accuracy during playback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If binaural or multi-channel recording systems are used to simulate the original acoustic environment, then directionality and realism are improved, but the accuracy of sound reproduction varies due to differences between recording and playback technologies
Solution Approach 1:
The patent applies parameter changes by computing equalization signals that adjust frequency responses based on characterized audio colorations from microphones, playback devices, and headphones. The system modifies audio parameters dynamically to compensate for variations in recording and playback equipment, thereby maintaining high accuracy across different devices while preserving the directional and realistic characteristics of binaural recordings.
2Measurement precision
If proxy devices like dummy heads are used to record sound as heard by a listener, then directionality is enhanced, but the system cannot account for variations in actual listener anatomy and headphone types
Solution Approach 1:
The patent uses copying by creating database entries that store characterized audio colorations for different microphone types, playback devices, and headphone models. Instead of requiring physical replication of every possible configuration, the system copies and stores measurement data from representative samples, then retrieves appropriate calibration parameters when needed, simplifying the overall system while maintaining precision.
Solution Approach 2:
The patent applies preliminary action by pre-characterizing audio colorations from microphones, playback devices, and headphones before actual recording and playback sessions. These characterized parameters are stored in databases and used to compute equalization signals in advance, eliminating the need for complex real-time calibration during actual use and reducing system complexity.
3Measurement precision
If equalization signals are computed to compensate for audio colorations, then sound accuracy is improved, but processing time and computational requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing equalization parameters in databases during offline characterization phases. The actual calibration process during playback only involves retrieving pre-computed parameters and applying them through standard audio processing, significantly reducing real-time computational requirements and processing time while maintaining high audio fidelity.
Data Source
AI summary
User headphones are calibrated in real time to improve the reproduction accuracy of recorded audio content. Microphones of a type used to record the audio content (including their orientation and recording characteristics) are characterized to indicate a first audio coloration. Audio playback devices of a type used to process the audio content are characterized to indicate a second audio coloration. Headphones of a type corresponding to the user headphones are characterized to indicate a third audio coloration. An equalization signal is computed based on the audio colorations, and is applied to calibrate the user headphones during playback of the audio content. A database of the characterizations is maintained so that calibration of different models of headphones using different playback devices can be accomplished for audio content recorded using different models of microphones.