Two-Channel Room Transfer Function Estimation Using Spectral Splitting
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Solution Overview
Problem
Current sound calibration methods for audio systems require user intervention and disrupt normal playback to estimate the Room Transfer Function (RTF), making them time-consuming and not suitable for automatic, perceptually-transparent operation in varying acoustic environments.
Innovation Solution
A method using spectral splitting with filter banks to generate uncorrelated calibration signals across channels, allowing for simultaneous RTF estimation without user intervention, using a single microphone positioned near the listener, and enabling periodic compensation for acoustic changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration signals are used for RTF estimation in a dedicated process applied to each loudspeaker separately, then measurement precision is improved, but productivity deteriorates due to time-consuming operation and user intervention requirements
Solution Approach 1:
The patent combines the calibration processes for multiple loudspeakers into a single simultaneous operation. By playing back uncorrelated calibration signals from all loudspeakers at once and using a single microphone to capture all responses, the system merges what would traditionally be separate sequential measurements into one integrated process, thereby improving productivity while maintaining measurement precision through spectral splitting techniques.
Solution Approach 2:
The patent applies spectral splitting to divide the frequency spectrum into different bands that can be separately analyzed for each loudspeaker. This segmentation allows the system to extract individual RTF information from the combined microphone signal, enabling simultaneous multi-channel calibration without sacrificing the precision that would traditionally require separate measurements.
2Measurement precision
If calibration signals are used for RTF estimation, then measurement precision is improved, but ease of operation deteriorates due to disruption of normal playback and user intervention
Solution Approach 1:
The patent enables continuous calibration operation by using uncorrelated calibration signals that can be played back simultaneously with normal audio content. The spectral splitting technique allows the system to continuously extract RTF information from the combined signal without interrupting the useful action of normal playback, making the calibration process transparent and convenient for users.
Solution Approach 2:
The system performs automatic RTF estimation without requiring user intervention. The calibration process is self-service in nature, where the system autonomously plays back calibration signals, captures microphone responses, processes the spectral information, and updates the equalization parameters without user involvement, thereby improving ease of operation.
3Ease of operation
If non-dedicated source signals are used for RTF estimation during playback, then ease of operation is improved, but measurement precision deteriorates due to longer averaging times required
Solution Approach 1:
The patent transforms the calibration approach by changing the parameters of the calibration signals to be uncorrelated across different loudspeakers. This parameter change allows the system to distinguish individual loudspeaker responses from the combined microphone signal through spectral splitting, achieving high measurement precision while maintaining the convenience of simultaneous playback without requiring longer averaging times.
Data Source
AI summary
A system and method for performing perceptually-transparent RTF estimation for a two-channel system with low estimation errors. The system includes two loudspeakers for the left and right channels positioned in a room and a single microphone, positioned in the vicinity of a listener in the room. The system performs spectral splitting using a filter bank and a complementary filter bank, to obtain separation in frequency between the two channels. Calibration signals being uncorrelated across the two channels are , generated using the original audio signals and the constructed filters. Then, the calibration signals are played back by the loudspeakers, instead of playback of the original audio signals. At the end, the system records the playback of the calibration signals by the microphone and simultaneously estimates the two-channel RTF using the recorded played back calibration signals.