Bone Conduction Speaker Noise Leakage Cancellation
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Solution Overview
Problem
Wearable devices with bone conduction speakers face challenges in minimizing sound leakage, which compromises user privacy and causes disturbance to bystanders, as vibrations from the speakers can be audible to others.
Innovation Solution
The integration of an active noise cancellation module using air conduction microphones to generate reference and error noise data, which is then used to create cancellation audio data that destructively interferes with sound leakage, combined with adaptive filtering techniques like the filtered-X least-mean-square algorithm to adapt to changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If bone conduction speaker vibrations are increased to improve audio output, then sound leakage increases, but user privacy is compromised
Solution Approach 1:
The patent captures the harmful sound leakage from the bone conduction speaker and converts it into a useful signal by using a microphone to record the leaked sound. This recorded leakage signal is then processed through adaptive filtering to generate anti-noise that cancels the original leakage, transforming the harmful effect into a beneficial noise cancellation mechanism that preserves user privacy while maintaining audio output quality
Solution Approach 2:
The system performs preliminary anti-action by generating cancellation signals in advance that are designed to destructively interfere with the sound leakage before it propagates. The adaptive filter continuously predicts and generates anti-noise signals that counteract the upcoming sound leakage, preventing privacy compromise before it occurs
2Power
If bone conduction speaker vibrations are increased to improve audio output, then sound leakage increases, but disturbance to bystanders increases
Solution Approach 1:
The patent transforms the harmful sound leakage that disturbs bystanders into a useful measurement signal. By recording the leaked sound with a microphone and processing it through adaptive filtering, the system generates cancellation signals that eliminate the disturbance to bystanders while preserving the intended audio output for the user
3Object-generated harmful factors
If active noise cancellation is added to reduce sound leakage, then user privacy is improved, but device complexity increases
Solution Approach 1:
The patent introduces a microphone as an intermediary element that captures the sound leakage from the bone conduction speaker. This intermediary device enables the noise cancellation system to measure and process the leakage signal without requiring direct modification of the speaker itself, thereby reducing overall system complexity while achieving effective privacy protection
Solution Approach 2:
The system implements feedback by continuously monitoring the sound leakage through the microphone and using adaptive filtering to adjust the cancellation signals in real-time. This feedback mechanism allows the system to automatically adapt to changing acoustic conditions and maintain effective noise cancellation without requiring complex manual configuration
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
This solution effectively reduces sound leakage, enhancing user privacy and minimizing disturbance to bystanders by ensuring that audio output remains private and is not inadvertently shared with the environment.
Implementation Method 1
The BCS comprises an actuator that provides a physical displacement responsive to a drive signal... the vibration is mechanically coupled to the user's skull
Implementation Method 2
a first air conduction microphone mounted in a temple of the HMWD... a second air conduction microphone mounted in a front bridge of the front frame
Implementation Method 3
generate cancellation audio data... The cancellation audio output... destructively interferes with the sound leakage
Data Source
AI summary
A head-mounted wearable device (HMWD) may incorporate bone conduction speakers (BCS) to generate audio output that is perceptible to a wearer. During operation, vibrations of the BCS may produce sound in the surrounding air that is perceptible to bystanders. An active noise cancellation module monitors the output and generates cancellation audio that is out of phase with the sound leaked by the BCS. An air conduction speaker emits the cancellation audio, producing destructive acoustic interference to the leaked sound. As a result, the user of the HMWD is able to hear audio clearly while bystanders are not.