Intra-aural Device Speech Enhancement in Noisy Environments
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Solution Overview
Problem
In noisy environments, existing communication technologies face challenges with low signal-to-noise ratio (SNR) for airborne speech and limited frequency bandwidth for bone and tissue conducted speech, making communication difficult, especially in industrial settings where noise levels are high and hearing protection devices are necessary.
Innovation Solution
An intra-aural device with an in-ear microphone and an outer-ear microphone uses adaptive filtering and non-linear bandwidth extension to enhance speech signals, denoise, and extend the frequency bandwidth, effectively removing residual noise and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a boom microphone is used to capture speech in noisy environments, then directional speech capture is achieved, but the signal-to-noise ratio deteriorates in excessively noisy environments
Solution Approach 1:
The patent introduces bone and tissue conduction as an intermediary mechanism to capture speech signals. Instead of relying solely on airborne sound waves that are contaminated by background noise, the system uses vibrations transmitted through the skull bones and tissues to reach the inner ear, providing a cleaner speech signal path that bypasses the noisy external environment.
Solution Approach 2:
The patent replaces the traditional acoustic mechanical system (boom microphone capturing airborne sound) with a biomechanical system (bone and tissue conduction). This substitution uses the body's own structural mechanics to transmit speech vibrations directly to the hearing mechanism, eliminating the need for external acoustic capture that is vulnerable to noise interference.
2Reliability
If bone conduction sensors are used to capture speech, then signal-to-noise ratio is improved, but frequency bandwidth is limited to less than 2 kHz
Solution Approach 1:
The patent merges two previously separate approaches into a single integrated system: bone and tissue conduction for high SNR speech capture, combined with electronic bandwidth extension techniques to recover the missing high-frequency information. This combination allows the system to simultaneously achieve both high signal-to-noise ratio and adequate frequency bandwidth for intelligible speech.
Solution Approach 2:
The patent applies parameter changes through signal processing techniques to extend the frequency bandwidth of the bone-conducted speech signal. By using spectral manipulation, harmonic generation, and other parametric methods, the system transforms the limited bandwidth signal (less than 2 kHz) into a wider bandwidth signal that preserves speech intelligibility and quality.
3Object-affected harmful factors
If circumaural HPDs with boom microphones are used, then hearing protection is provided, but compatibility with other personal protection equipment deteriorates
Solution Approach 1:
The patent replaces the external mechanical boom microphone system with an internal biomechanical sensing system. Bone and tissue conduction sensors can be integrated into the hearing protection device itself or positioned on the head, eliminating the need for external boom microphones that conflict with helmets, gas masks, and other personal protection equipment.
4Reliability
If bandwidth extension techniques are applied to bone and tissue conducted speech, then signal quality is enhanced, but computational complexity increases substantially
Solution Approach 1:
The patent employs computationally efficient bandwidth extension methods that use simpler, less resource-intensive algorithms. Rather than applying complex machine learning models or extensive signal processing chains, the system uses streamlined techniques such as harmonic generation and spectral replication that require minimal computational resources while still achieving effective bandwidth extension for speech enhancement.
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
The solution significantly enhances speech quality by improving the SNR and extending the frequency bandwidth, providing a simple and effective method for communication in noisy conditions, as demonstrated by gains in perceptual objective listening quality assessment and multiple stimuli hidden reference and anchor scores.
Implementation Method 1
speech captured through bone and tissue vibrations has been used to provide a signal with a higher SNR
Implementation Method 2
The adaptive filter is used to remove residual noise from the in-ear microphone signal
Implementation Method 3
The bandwidth extension process is then applied to extend the frequency bandwidth of the denoised signal
Data Source
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Figure 4A
AI summary
A method, and device, for enhancing speech generated from bone and tissue conduction of a user of an In-ear device in a noisy environment, the Intra-aural device having an in-ear microphone adapted to be in fluid communication with the ear canal of the user and an outer-ear microphone adapted to be in fluid communication with the environment outside the ear. The method comprises applying an adaptive filter on the in-ear microphone signal, using the outer-ear microphone signal as a reference for the ambient noise and interrupting the application of the adaptive filter to the In-ear microphone signal upon detecting speech by the user.