Headset Ambient Noise Reduction via Time-Varying Speech Filtering
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Solution Overview
Problem
Existing headsets struggle with ambient noise interference during two-way communication, as ambient noise is transmitted along with the user's voice, and confidential communications can be inadvertently shared, necessitating an improved ambient noise reduction system.
Innovation Solution
A headset with an ambient noise reduction block that continuously detects user speech, measures voice and ambient microphone signals, applies a time-varying filter to attenuate noise, and uses multiple microphones to enhance signal-to-noise ratio by subtracting attenuated ambient signals, ensuring coherence with the voice signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voice microphone is arranged close to the user's mouth to improve signal-to-noise ratio, then voice capture quality is improved, but ambient noise from the surrounding environment is still transmitted along with the voice
Solution Approach 1:
The patent segments the audio capture function into two separate microphones: a voice microphone positioned close to the mouth for capturing speech, and an ambient microphone positioned away from the mouth for capturing surrounding noise. This segmentation allows independent optimization of each microphone's position and function, resolving the contradiction between close positioning for voice capture and distance positioning for noise capture.
Solution Approach 2:
The patent introduces a digital signal processor as an intermediary that receives signals from both microphones and applies adaptive filtering algorithms. This intermediary processes the voice microphone signal by subtracting estimated ambient noise components, thereby removing harmful ambient noise while preserving the desired voice signal.
2Object-generated harmful factors
If an ambient microphone is positioned away from the user's mouth to capture ambient noise, then ambient noise capture is improved, but the microphone becomes more susceptible to interference from distant sound sources
Solution Approach 1:
The patent implements a feedback mechanism where the digital signal processor continuously analyzes the ambient microphone signal to identify and estimate ambient noise components. This estimated noise is then fed back into the signal processing chain to be subtracted from the voice microphone signal, creating a closed-loop system that adaptively reduces ambient noise while minimizing interference from distant sources.
Solution Approach 2:
The patent employs dynamic adaptive filtering where the filter coefficients are continuously adjusted based on real-time analysis of the ambient noise characteristics. This dynamic adaptation allows the system to distinguish between relevant ambient noise to be removed and distant sound sources that should be preserved, resolving the contradiction between ambient noise capture and interference rejection.
3Object-generated harmful factors
If a time-varying filter is applied to remove ambient noise from the voice signal, then ambient noise reduction is improved, but the system complexity increases
Solution Approach 1:
The patent applies partial action by selectively processing only the ambient noise components rather than the entire audio signal. The digital signal processor identifies and removes only the specific frequency ranges and temporal patterns characteristic of ambient noise, leaving the voice signal largely untouched. This selective approach reduces computational complexity compared to processing the complete signal spectrum.
Solution Approach 2:
The patent performs preliminary action by pre-characterizing the ambient noise profile during periods when the user is not speaking. This pre-acquired noise characterization is stored and later applied during speech segments, avoiding the need for complex real-time analysis during active communication and thereby reducing overall system complexity.
Data Source
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AI summary
A headset (1; 101) adapted to transmitting an outgoing audio signal (Tx) and comprising a voice microphone (12) and at least one ambient microphone (21). The headset comprises an ambient noise reduction block (ANR), which is adapted to reduce the level of ambient noise in the outgoing audio signal (Tx). The ambient noise reduction block (ANR) includes the measuring the levels of the voice microphone signal (X) and ambient microphone signal (Y) to estimate a characteristic constant level drop between the voice microphone signal (X) and the ambient microphone signal (Y), which is characteristic for the headset user talking. A time-varying filter passes the voice microphone signal (X), when the level difference is larger than characteristic constant level drop (CLD) and attenuates the voice microphone signal (X), if the level difference is below characteristic constant level drop.