Audio Signal Synchronization Using Attack-Based Cross-Correlation
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Solution Overview
Problem
Conventional audio signal synchronization techniques are inadequate for aligning dissimilar audio signals recorded by multiple devices, especially in environments with room reverberation and when signals have wide peaks or multiple peaks of similar amplitude, leading to timing errors and uncertainties.
Innovation Solution
The method involves determining a first delay based on cross-correlation of waveforms and a second delay based on cross-correlation of attacks in audio signals, improving alignment quality by synchronizing audio signals using the attack-based delay, which reduces uncertainty and handles dissimilar signals more accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional cross-correlation analysis of waveforms is used for synchronization, then the method is simple to implement, but it produces timing errors in environments with room reverberation and fails when signals have wide peaks or multiple peaks of similar amplitude
Solution Approach 1:
The patent extracts attack information from the audio signals by computing the derivative of the envelope. This separates the attack detection task from the full waveform analysis, allowing the system to focus on the most distinctive and reliable features for synchronization while ignoring reverberation effects that affect the overall waveform shape.
Solution Approach 2:
The patent applies different processing strategies to different parts of the audio signal. Instead of treating the entire waveform uniformly, it identifies and processes attack regions separately using derivative-based detection, while using standard cross-correlation for other portions. This localized approach improves reliability in reverberant environments.
2Reliability
If attack-based cross-correlation is used for synchronization, then the robustness against reverberation and handling of dissimilar signals is improved, but the computational complexity increases due to envelope computation and derivative calculation
Solution Approach 1:
The patent computes the envelope of the audio signal before performing cross-correlation. This preliminary processing step transforms the signal into a form where attacks are more distinct and easier to detect, simplifying the subsequent synchronization task despite adding an initial computational step.
Solution Approach 2:
The patent replaces direct waveform comparison with a transformed representation based on envelope derivatives. This substitution changes the mechanical approach from comparing raw waveforms to comparing extracted attack features, which are more robust to reverberation and signal dissimilarity.
3Ease of manufacture
If standard waveform cross-correlation is used, then the computational process is straightforward, but it leads to large uncertainties when signals exhibit wide peaks or multiple peaks of similar amplitude
Solution Approach 1:
The patent introduces attack information as an intermediary element between the raw audio signals and the cross-correlation process. By detecting attacks through envelope derivatives and using these as reference points for synchronization, the system resolves ambiguities caused by wide or multiple peaks in the original waveforms.
Data Source
AI summary
Methods, systems, and computer program products for synchronizing audio signals captured by multiple independent devices during an audio event are described. Multiple recording devices, e.g. several smartphones, record the audio event. A computer system receives audio signals from the devices. The system determines a first delay between two audio signals based on cross-correlation of waveforms of the two audio signals. Subsequently, the system detects attacks that are present in each audio signal by computing the derivative of a respective envelope for each audio signal. The system determines a second delay between the two audio signals based on cross-correlation of attacks of the two audio signals. The system synchronizes the audio signals using the second delay upon determining that using the second delay improves sound quality over using the first delay.