Adaptive Howling Suppression in Wearable Audio ANC Systems
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Solution Overview
Problem
Active noise control (ANC) systems in wearable audio components often experience howling due to changes in the acoustic channel, such as when a user wraps their hands around earbuds, creating a sealed acoustic space that leads to feedback loops and high-pitched squealing noises.
Innovation Solution
The system adaptively suppresses howling by detecting whether the wearable audio component is being worn and adjusting ANC parameters accordingly. Upon detecting howling, the system pre-suppresses the audio signature, then uses on-ear or off-ear tuning settings to cycle through suppression stages until ANC output can be restored without howling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ANC is disabled to suppress howling, then howling is suppressed, but ANC functionality is lost
Solution Approach 1:
The system dynamically adjusts ANC output based on detected wear state. When on-ear condition is detected, ANC is activated with appropriate parameters; when off-ear condition is detected, ANC is suppressed. This dynamic adaptation allows the system to maintain ANC functionality when needed while suppressing howling when the device is not properly worn.
Solution Approach 2:
The system uses feedback from sensors (accelerometers, microphones, capacitive sensors) to detect the wear state and continuously monitors acoustic feedback. Based on this feedback, the system adjusts ANC parameters in real-time, enabling it to distinguish between legitimate ANC operation and howling conditions, thereby maintaining functionality while suppressing harmful feedback.
2Object-affected harmful factors
If ANC output is reduced to suppress howling feedback, then howling is suppressed, but ANC effectiveness is reduced
Solution Approach 1:
The system applies different ANC output levels to different frequency ranges and spatial directions. By analyzing the acoustic feedback characteristics, the system can suppress howling in specific frequency bands while maintaining full ANC effectiveness in other bands, thereby locally optimizing the balance between suppression and effectiveness.
3Speed
If ANC parameters are adjusted quickly to suppress howling, then howling suppression speed is improved, but system stability may be compromised
Solution Approach 1:
The system employs periodic monitoring of wear state and acoustic feedback, adjusting ANC parameters at regular intervals rather than continuously. This periodic action allows the system to respond quickly to changes in wear state while maintaining stability by avoiding excessive or continuous parameter adjustments that could destabilize the control loop.
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 approach effectively suppresses howling by quickly identifying and adapting to the wear state of the earbuds, restoring ANC functionality without introducing distortions or compromising the frequency response.
Implementation Method 1
The ambient noise and anti-noise signal cancel each other acoustically
Implementation Method 2
the sound from the earbud's speakers to feed back to the earbud's microphones and to be re-amplified and re-emitted in a feedback loop
Data Source
AI summary
Adaptive howling suppression is provided for active noise control (ANC) systems of wearable audio components (WACs), such as earbuds, based on detecting whether the WACs are presently being worn. Upon first detecting howling, embodiments can pre-suppress the howling audio signature by reducing ANC output. Then, embodiments detect whether the WAC is presently on-ear (worn) or off-ear and attempt to fully suppress the howling using different parameters, based on this detection. For example, if on-ear, embodiments use on-ear tuning settings to cycle through a set of suppression stages until ANC output can be restored without howling; if off-ear, embodiments use off-ear tuning settings to cycle through the set of suppression stages until ANC output can be restored without howling. Once ANC output can be restored without howling, the system can be released to a normal idle state.