Virtual Microphone Noise Rejection in Multi-Pod Conferencing
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Solution Overview
Problem
Conferencing systems face challenges with echo cancellation and noise rejection, particularly in multi-pod setups where common-mode noise and echo can be significant, affecting audio quality and participant interaction.
Innovation Solution
The implementation of a virtual microphone system that includes three bi-polar microphones positioned at 120-degree intervals, coupled with echo cancellation and microphone gating mechanisms to determine the best microphone to activate, reducing common-mode noise and improving audio processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple physical microphones are used in each pod to improve audio coverage, then audio quality and noise rejection are improved, but device complexity and processing requirements increase
Solution Approach 1:
The patent combines multiple physical microphones (typically three) into a single virtual microphone through digital signal processing. The pod processor correlates signals from multiple microphones and sums them to create one virtual microphone signal per pod, reducing the total number of microphone signals from N pods × 3 microphones to N virtual microphone signals while maintaining improved noise rejection and audio quality
Solution Approach 2:
The virtual microphone acts as an intermediary between the multiple physical microphones and the conferencing system. Instead of processing individual microphone signals directly, the system uses virtual microphones as intermediate representations that encapsulate the combined acoustic information from multiple physical sensors, simplifying downstream processing
2Measurement precision
If echo cancellation processing is applied to improve audio clarity, then audio quality is improved, but processing time and computational load increase
Solution Approach 1:
The system performs preliminary echo cancellation by having the pod processor correlate the loudspeaker signal with the virtual microphone signal and generate an echo estimate before the audio is transmitted. This pre-processing removes echo components in advance, reducing the need for complex real-time echo cancellation at the base unit and decreasing overall processing time
Solution Approach 2:
The echo cancellation function is segmented and distributed: the pod processor handles local echo cancellation for its own pod by correlating local loudspeaker and microphone signals, while the base unit handles system-wide echo cancellation. This division of labor reduces the computational burden on any single processor and speeds up overall processing
3Object-affected harmful factors
If microphone gating is used to select the best microphone to reduce noise, then noise rejection is improved, but processing complexity increases
Solution Approach 1:
The microphone gating mechanism monitors parameters such as signal level, noise floor, and signal-to-noise ratio for each virtual microphone and dynamically changes the gating state (on/off or gain adjustment) based on these parameters. This automatic parameter-based control improves noise rejection by silencing or attenuating microphones in noisy environments while keeping the processing relatively simple through threshold-based decision logic
Data Source
AI summary
This disclosure describes a virtual microphone for reducing common-mode noise for an individual pod in a multi-pod conferencing system that includes a base and a plurality of pods for local conference participants to communicate with remote conference participants. The described virtual microphone includes pod processor means and a loudspeaker that couples to a digital to analog converter that converts digital audio to analog audio, where the loudspeaker couples to the pod processor means. In addition, the virtual microphone includes three physical bi-polar microphones positioned at 120-degree intervals in the horizontal resting plane of the pod, where each individual physical microphone connects to a pair of audio ports with each audio port being equal distance from the loudspeaker, and where the physical microphones couple to analog to digital converting means, and further where the physical microphones couple to the pod processor means. Further, the virtual microphone includes virtual microphone means. And, the virtual microphone includes pod echo cancellation means. Further, the virtual microphone includes microphone gating means using a loudness value, a quietness counter, and a noise floor value. And further, the virtual microphone also has the individual pod using the microphone gating means to gate on or off the virtual microphone.