Dynamic Feedforward Microphone Selection for Stable Hear-Through ANR
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Solution Overview
Problem
Active noise reduction (ANR) devices with multiple feedforward microphones face instability in the active hear-through mode due to acoustic coupling between microphones and the acoustic transducer, leading to high-frequency ringing and user discomfort.
Innovation Solution
A controller dynamically selects different subsets of microphones for ANR and hear-through modes, excluding microphones acoustically coupled to the transducer to prevent instability, and adjusts gain to maintain performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple feedforward microphones are used in ANR devices, then noise cancellation performance is improved, but acoustic coupling between microphones and acoustic transducer causes instability in hear-through mode
Solution Approach 1:
The patent segments the microphones into different subsets based on their acoustic coupling characteristics. A first subset of microphones is selected for ANR mode while a second subset is selected for hear-through mode, excluding microphones that are acoustically coupled to the acoustic transducer. This segmentation allows the system to optimize performance for each mode separately, using microphones that provide good noise cancellation for ANR mode while avoiding microphones that cause instability in hear-through mode.
Solution Approach 2:
The patent implements dynamic controller that adapts the microphone subset selection based on the operational mode. The controller dynamically switches between different microphone subsets depending on whether the device is in ANR mode or hear-through mode, and can adjust gain parameters in real-time. This dynamic adaptation allows the system to maintain stability across different operating conditions while optimizing performance for each specific mode.
2Ease of operation
If microphones acoustically coupled to the transducer are included in hear-through mode, then ambient sound transmission is improved, but high-frequency ringing and user discomfort occur
Solution Approach 1:
The patent extracts or removes acoustically coupled microphones from the hear-through mode operation. The controller identifies microphones that are acoustically coupled to the acoustic transducer and excludes them from the second subset used for hear-through mode. This extraction eliminates the source of high-frequency ringing and user discomfort while preserving the ability to transmit ambient sounds through the remaining microphones in the subset.
Solution Approach 2:
The patent applies different quality criteria to different microphone subsets. For ANR mode, microphones are selected based on their ability to capture ambient noise effectively. For hear-through mode, microphones are selected based on their ability to transmit ambient sounds while avoiding acoustic coupling with the transducer. This local quality differentiation ensures that each microphone subset is optimized for its specific function, preventing harmful effects in hear-through mode while maintaining good performance in ANR mode.
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
Improves ANR performance without negatively impacting the stability of the active hear-through mode, ensuring better noise cancellation and ambient sound transmission.
Implementation Method 1
a plurality of microphones, wherein each of the plurality of microphones is usable for capturing ambient audio to generate input signals
Implementation Method 2
detect that a particular microphone of the second subset is acoustically coupled to an acoustic transducer of the ANR device
Data Source
AI summary
Technology described in this document can be embodied in an earpiece of an active noise reduction (ANR) device. The earpiece includes a plurality of microphones, wherein each of the plurality of microphones is usable for capturing ambient audio to generate input signals for both an ANR mode of operation and a hear-through mode of operation of the ANR device. The earpiece further includes a controller configured to: process a first subset of microphones from the plurality of microphones to generate input signals for the ANR mode of operation and process a second subset of microphones from the plurality of microphones to generate input signals for the hear-through mode of operation. The second subset of microphones excludes a first microphone from the plurality of microphones located closest to a noise pathway of the earpiece.