Microphone Audio Mixing Using Room Impulse Response Estimation
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Solution Overview
Problem
Audio systems face challenges in mixing near-field and far-field microphone signals due to the differing effects of the recording space, leading to audible artefacts and non-natural sounding audio content, as near-field signals have a higher signal-to-noise ratio and are less affected by the recording environment compared to far-field signals.
Innovation Solution
The use of room impulse response (RIR) filters to model the effect of the recording space on both near-field and far-field audio signals, combined with recursive least squares (RLS) algorithms for real-time estimation, allows for the separation and processing of near-field noise signals, including whitening, normalizing, and de-correlating to generate residual and ambient signals, and the injection of noise kernels to improve RIR estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If near-field microphone signals are used for audio mixing, then the signal-to-noise ratio is improved and the audio is less affected by recording environment, but the effect of the recording space cannot be properly modeled leading to audible artifacts
Solution Approach 1:
The patent segments the audio signal processing into near-field and far-field components, applying different processing techniques to each. The near-field signal is processed separately to preserve its high signal-to-noise ratio characteristics, while the far-field signal is used to capture room impulse response characteristics. This segmentation allows the system to maintain the advantages of both signal types without combining their disadvantages.
Solution Approach 2:
The patent introduces an intermediary processing stage that models the room impulse response and applies it to the near-field signal. This intermediary model acts as a bridge, transferring the spatial characteristics from the far-field signal to the near-field signal, thereby enabling the near-field audio to reflect the recording space effects without directly using the noisy far-field signal.
2Loss of information
If far-field microphone signals are used to model recording space effects, then the room impulse response can be captured, but the signal-to-noise ratio decreases and the audio is more affected by the recording environment
Solution Approach 1:
The patent extracts the room impulse response characteristics from the far-field signal by analyzing its spatial properties and temporal reflections. This extracted information is then separated from the noisy far-field audio content, allowing the system to utilize only the beneficial spatial characteristics while discarding the noise and environmental artifacts present in the original far-field signal.
Solution Approach 2:
Instead of directly using the noisy far-field signal, the patent creates a cleaned copy of the room impulse response characteristics. This copied information is then applied to the near-field signal, effectively replicating the spatial effects without introducing the noise and environmental degradation present in the original far-field recording.
3Productivity
If simple audio mixing is used, then the processing is simpler and faster, but the audio quality is lower with audible artifacts and non-natural sounding content
Solution Approach 1:
The patent performs preliminary analysis of the far-field signal to extract room impulse response characteristics before the actual mixing process. This pre-processing step creates a reusable model of the recording space that can be applied during mixing, avoiding the need for complex real-time calculations and enabling high-quality processing at reduced computational cost.
Solution Approach 2:
The patent transforms the audio processing from simple amplitude mixing to a more sophisticated approach that manipulates temporal and spectral parameters. By applying room impulse response convolution and adjusting spatial parameters, the system enhances audio quality and naturalness while maintaining computational efficiency through parameter-based processing rather than sample-by-sample operations.
Data Source
AI summary
An apparatus, method and computer program is described comprising: receiving one or more near-field audio source signals from one or more near-field microphones; providing one or more near-field noise signals; receiving a far-field audio signal from an array comprising one or more far-field microphones, wherein the far-field audio signal includes audio components from the one or more near-field audio source signals and the one or more near-field noise signals; and determining room impulse filter responses for the one or more near-field audio source signals and the one or more near-field noise signals.