Beamforming Audio Null Steering for Stereo Separation
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Solution Overview
Problem
Portable electronic devices with audio and video recording capabilities face challenges in implementing stereo audio recording due to space and cost constraints, as they often rely on fewer, less expensive omnidirectional microphones rather than directional microphones, which are more expensive and difficult to package.
Innovation Solution
The use of two microphones positioned at opposite ends of the device, with beamforming techniques such as delay and sum processing, to create steerable directional patterns with nulls, allowing for effective stereo audio acquisition and noise cancellation, even when recording sources are distant from the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If directional microphones are used for stereo recording, then audio recording quality and stereo separation are improved, but device cost and complexity increase
Solution Approach 1:
The patent divides the audio processing function into multiple omnidirectional microphones (at least two) positioned at different locations in the device, with each microphone capturing audio from all directions. The signal processing is then segmented to create directional patterns through beamforming algorithms, separating the directional functionality from the physical microphone structure.
Solution Approach 2:
The patent replaces the mechanical solution of using physical directional microphones with an electronic/software-based beamforming system. Instead of relying on the physical orientation and directional characteristics of microphone elements, the system uses digital signal processing to create steerable directional patterns and nulls, substituting mechanical complexity with computational processing.
2Measurement precision
If directional microphones are used for stereo recording, then stereo separation is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent segments the stereo recording function across multiple omnidirectional microphones positioned at standard locations in the device housing, rather than requiring specialized directional microphone assemblies. This segmentation allows each microphone to be manufactured and positioned independently using standard manufacturing processes.
Solution Approach 2:
The patent employs inexpensive omnidirectional microphones instead of costly directional microphones. These simple omnidirectional elements are easier and cheaper to manufacture, and their directional capabilities are achieved through software processing rather than expensive specialized hardware, reducing overall manufacturing cost and difficulty.
3Measurement precision
If more microphones are added for stereo recording, then audio acquisition quality is improved, but device space requirements increase
Solution Approach 1:
The patent makes the existing microphones in the device serve multiple functions: they are used for voice calls, environmental noise pickup, and stereo audio recording simultaneously. By positioning omnidirectional microphones at standard locations and using beamforming processing, the same hardware resources achieve stereo recording capabilities without requiring dedicated additional microphone elements.
Solution Approach 2:
The patent merges the stereo recording function with the existing microphone system used for other audio functions. Instead of adding separate dedicated stereo microphones, the system combines multiple omnidirectional microphones already present in the device, using signal processing to extract stereo information from their combined outputs.
4Device complexity
If omnidirectional microphones are used instead of directional microphones, then device cost is reduced, but noise cancellation capability deteriorates
Solution Approach 1:
The patent performs preliminary signal processing by creating beamformed signals with predetermined directional patterns and nulls before final audio output. The system pre-calculates and applies delay and gain adjustments to microphone signals to establish directional sensitivity and noise-rejection nulls in advance, enabling effective noise cancellation with omnidirectional microphones.
Solution Approach 2:
The patent substitutes the passive noise rejection capability of directional microphones with active electronic noise cancellation through beamforming. Instead of relying on the physical directional characteristics of microphone elements to reject noise, the system uses digital signal processing to dynamically create nulls in the beamforming patterns, electronically canceling noise from specific directions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables high-quality stereo audio recording with improved stereo separation and noise cancellation using existing omnidirectional microphones, enhancing the audio recording capabilities of portable devices without the need for additional or more expensive microphones.
Implementation Method 1
a beamform processor, which generates a right beamformed audio signal and a left beamformed audio signal, each having a first-order directional pattern
Implementation Method 2
delay and sum processing, to create steerable directional patterns with nulls
Implementation Method 3
a first microphone, which generates a first signal in response to incoming sound, and a second microphone, which generates a second signal in response to the incoming sound
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
An electronic apparatus (100) is provided having a front side and a rear side oriented in opposite directions along a first axis, and a right-side and a left-side oriented in opposite directions along a second axis that is perpendicular to the first axis. A null control signal (565) is generated based on an imaging signal (585). A first microphone (530) located near the right-side of an electronic apparatus generates a first signal, and a second microphone (520) located near the left-side of the electronic apparatus generates a second signal. The first and second signals are processed, based on the null control signal, to generate a right beamformed audio signal (552) having a first directional pattern having at least one first null, and a left beamformed audio signal (554) having a second directional pattern having at least one second null. A first angular location (a) of the at least one first null and a second angular location (ß) of the at least one second null are steered based on the null control signal.