Earpiece Calibration Using a Controlled Acoustic Charging Case
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Solution Overview
Problem
Earpieces of audio devices, such as earbuds and headphones, experience variations in microphone sensitivity due to manufacturing inconsistencies and environmental factors, leading to suboptimal performance over time.
Innovation Solution
A controlled acoustic environment within a case, such as a charging case, is used to recalibrate earpiece microphones and drivers, compensating for sensitivity changes due to aging, damage, or environmental conditions, ensuring balanced performance and user experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If earpieces are placed in a charging case for storage, then the earpieces are protected and charged, but the acoustic environment becomes unstable and unknown, preventing accurate calibration
Solution Approach 1:
An acoustic cavity is introduced as an intermediary element within the charging case to provide a stable, controlled acoustic environment. The cavity acts as a mediator between the earpiece and the external environment, ensuring consistent acoustic conditions for calibration while maintaining the protective and charging functions of the case.
Solution Approach 2:
The acoustic cavity is designed with specific geometric parameters (volume, shape, positioning) that are optimized to provide a stable acoustic environment. By controlling these physical parameters, the system ensures repeatable calibration conditions without requiring complex active control mechanisms.
2Measurement precision
If microphones are calibrated during manufacture using artificial heads, then initial sensitivity is optimized, but sensitivity drifts over time due to environmental conditions and aging
Solution Approach 1:
The system performs preliminary calibration checks automatically whenever the earpiece is placed in the charging case. This preliminary action detects sensitivity drift before it significantly impacts performance, allowing for timely compensation through trim control adjustments.
Solution Approach 2:
The system uses the earpiece's own microphone to measure the acoustic response within the controlled cavity, creating a feedback loop. The measured sensitivity information is used to automatically adjust the trim control, compensating for drift without requiring external calibration equipment or user intervention.
3Reliability
If trim control is used to adjust microphone gain, then sensitivity variations are compensated, but the system complexity increases
Solution Approach 1:
The earpiece performs its own calibration using its built-in microphone and the controlled acoustic cavity. The system automatically measures its own sensitivity, computes the necessary trim control adjustments, and applies the compensation without requiring external calibration equipment or complex processing systems.
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 calibration maintains optimal audio quality and active noise reduction by adjusting gain settings based on real-time measurements, addressing sensitivity variations and ensuring consistent performance across earpieces.
Implementation Method 1
The surface of the acoustic cavity can be formed using a relatively rigid material that provides relatively high reflection and/or relatively low absorption of acoustic waves
Implementation Method 2
an acoustic driver that generates a sound wave to be heard by the user
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
An audio system comprises: a first earpiece comprising at least one acoustic driver, and circuitry that comprises at least one microphone; a housing configured to receive the first earpiece and enclose around the first earpiece; an acoustic cavity within the housing configured to provide a predetermined volume that is acoustically coupled to the acoustic driver when the first earpiece is housed within the housing. The first earpiece or the housing comprises circuitry configured to: (1) measure a response from the microphone to an acoustic wave, and (2) calibrate the circuitry based at least in part on the measured response.