On-Ear Detection Using Dual Microphones and Probe Signals
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Solution Overview
Problem
Existing headset systems face challenges in accurately determining whether they are worn on or in the user's ear, leading to false positives due to ambient noise and other environmental factors, which affects Active Noise Cancellation and other signal processing functions.
Innovation Solution
A hybrid on ear detection method using dual microphones, one internal and one external, and a processor that generates a probe signal to compare resonance, reducing false positives by analyzing the power levels and resonance of the signals from both microphones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sense microphone is used to detect acoustic sound inside the headset, then on ear detection can be achieved, but false positives occur due to loud ambient noise from traffic and other noise sources
Solution Approach 1:
A probe signal is introduced as an intermediary to mediate the detection process. The probe signal serves as a known reference that passes through the ear canal, allowing the system to distinguish between actual ear canal resonance and ambient noise. This intermediary signal enables reliable on-ear detection even in noisy environments by providing a controlled reference point for comparison.
Solution Approach 2:
The system uses feedback by comparing the probe signal sent through the ear canal with the signal received by the sense microphone. This feedback mechanism allows the processor to analyze the resonance characteristics and determine whether the headset is on-ear by evaluating how the ear canal modifies the probe signal, thereby reducing false positives caused by ambient noise.
2Reliability
If Active Noise Cancellation is continuously active, then noise cancellation function is maintained, but power consumption increases even when headset is not worn
Solution Approach 1:
Instead of continuous operation, the system performs periodic on-ear detection using probe signals at specified intervals. This periodic action allows the noise cancellation function to be activated only when needed (when the headset is detected as on-ear), significantly reducing power consumption while maintaining reliable noise cancellation functionality when required.
Solution Approach 2:
The noise cancellation system transitions from a static continuous operation mode to a dynamic mode where it is activated or deactivated based on real-time detection of headset wear status. This dynamic behavior allows the system to adapt its power consumption to actual usage conditions, maintaining functionality when needed while conserving energy when not in use.
3Measurement precision
If dedicated sensors such as capacitive, optical or infrared sensors are used, then on ear detection can be achieved, but device complexity increases
Solution Approach 1:
The existing microphones in the headset are made multi-functional by using them both for their primary purpose (audio capture) and for on-ear detection through probe signal analysis. This universality eliminates the need for dedicated sensors, reducing device complexity while maintaining on-ear detection capability. The same hardware components serve multiple functions, avoiding additional complexity.
Solution Approach 2:
The headset system performs its own on-ear detection using its existing audio components (microphones and speakers) without requiring external or dedicated detection sensors. The probe signal method allows the system to self-diagnose its wear status using resources already present in the device, thereby avoiding additional complexity that would arise from adding specialized sensors.
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 enhances the accuracy of determining whether the headset is on or off the ear, reducing false positives and improving the reliability of audio processing functions like Active Noise Cancellation.
Implementation Method 1
determine that the on ear status of the earbud cannot be sufficiently determined, generate a signal for acoustic playback from a speaker configured to be positioned within the earbud, receive a second microphone signal from the first microphone input, and compare the second microphone signal to the generated signal to determine the on ear status of the earbud
Data Source
AI summary
Described embodiments generally relate to a signal processing device for on ear detection for an earbud. The device comprises a first microphone input for receiving a microphone signal from a first microphone, the first microphone being configured to be positioned within an ear of a user when the earbud is being worn; a second microphone input for receiving a microphone signal from a second microphone, the second microphone being configured to be positioned outside the ear of the user when the earbud is being worn; a signal generator configured to generate a signal for acoustic playback from a speaker configured to be positioned within the earbud; and a processor. The processor is configured to receive at least one first microphone signal from each of the first microphone input and the second microphone input, and compare the first microphone signals to determine the on ear status of the earbud; determine that the on ear status of the earbud cannot be sufficiently determined, generate a signal for acoustic playback from the speaker, receive a second microphone signal from the first microphone input, and compare the second microphone signal to the generated signal to determine the on ear status of the earbud.