Wearable Audio Occlusion Reduction with Body-Vibration Feedforward
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Solution Overview
Problem
Wearable audio devices, such as earbuds, cause an occlusion effect where users perceive their own voice as significantly louder and unnatural due to vibrations traveling through bone and tissue, increasing sound pressure at low frequencies.
Innovation Solution
A noise reduction system incorporating a feedforward sensor to detect body conducted vibrations, an audio controller to generate a feedforward cancellation signal, and an acoustic driver to cancel sound pressure while playing audio data, optionally with feedback and external feedforward sensors to further reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the ear canal is occluded by the earbud to provide audio playback, then audio isolation is improved, but the occlusion effect causes the user's own voice to be perceived as significantly louder and unnatural
Solution Approach 1:
The system applies preliminary anti-action by using the feedforward sensor to detect body-conducted vibrations before they fully manifest as occlusion effect, and generating a cancellation signal that preemptively counteracts the harmful vibrations. The feedforward controller processes the detected vibrations and generates anti-phase signals that cancel the occlusion effect before it reaches the ear canal wall.
Solution Approach 2:
The feedforward sensor acts as an intermediary element that detects body-conducted vibrations separately from the acoustic driver's output. By placing the sensor on the exterior surface of the housing rather than inside the ear canal, it mediates between the source of vibrations and the user's ear, allowing detection and cancellation without interfering with normal audio playback.
2Measurement precision
If a feedback sensor is used to capture sound within the ear canal, then feedback cancellation can be achieved, but the sensor may detect both audio playback and occlusion effect vibrations simultaneously making separation difficult
Solution Approach 1:
The system segments the vibration detection function by separating the feedforward sensor from the acoustic driver path. The feedforward sensor is positioned on the exterior housing surface to detect only body-conducted vibrations, while the acoustic driver handles audio playback independently. This segmentation allows each component to perform its function without interference, simplifying signal processing.
Solution Approach 2:
The system replaces the traditional acoustic feedback measurement approach with a mechanical vibration detection approach. Instead of using a microphone to detect sound pressure from the user's voice, the feedforward sensor directly detects mechanical vibrations conducted through the skull and jaw bones. This mechanical substitution provides a cleaner signal that is easier to process and cancel.
3Object-generated harmful factors
If the feedforward sensor is positioned to detect body conducted vibrations on the exterior housing surface, then occlusion effect cancellation is improved, but the sensor may inadvertently detect vibrations from the acoustic driver
Solution Approach 1:
The system applies local quality by positioning the feedforward sensor at a specific location on the exterior housing surface where body-conducted vibrations are strongest while acoustic driver vibrations are weakest. The sensor is placed away from the acoustic driver to minimize coupling, and the feedforward controller is configured to filter out frequencies characteristic of the acoustic driver output, preserving only the body-conducted vibration information needed for occlusion effect cancellation.
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 system effectively reduces the occlusion effect by canceling sound pressure, providing clear audio playback and minimizing unnatural voice amplification.
Implementation Method 1
The feedforward sensor is arranged to detect body conducted vibrations, such as vibrations of a wall of an ear canal of a user
Implementation Method 2
The acoustic driver then generates audio based on the audio output signal
Implementation Method 3
The feedback sensor may be arranged to capture sound within the ear canal of the user, including the audio generated by the acoustic driver
Data Source
AI summary
A noise reduction system including a feedforward sensor, an audio controller, and an acoustic driver is provided. The feedforward sensor is arranged to detect body conducted vibrations. The feedforward sensor is configured to generate a feedforward signal based on the detected vibrations. The audio controller is communicatively coupled to the feedforward sensor. The audio controller is configured to generate an audio output signal based on the feedforward signal and a command signal. The acoustic driver is configured to render audio based on the audio output signal. In some examples, the noise reduction system further includes a feedback sensor arranged to capture sound within an ear canal of a user. The feedback sensor is configured to generate a feedback signal based on the captured sound. The audio output signal is generated further based on the feedback signal.