Speaker Impedance Monitoring for Ear Pressure Detection
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Solution Overview
Problem
Mobile devices' noise cancellation performance varies with the distance between the speaker and the user's ear due to changes in acoustic coupling, affecting audio output quality.
Innovation Solution
Measuring the impedance of the speaker to determine the pressure applied between the device and the ear, which is used to adjust the adaptive noise cancellation (ANC) algorithm and linearize the speaker output, ensuring optimal noise cancellation based on the user's ear position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the speaker is placed closer to the user's ear, then the acoustic coupling improves and noise cancellation performance improves, but the impedance varies and requires dynamic adjustment of processing
Solution Approach 1:
The system dynamically adjusts the adaptive noise cancellation processing based on real-time impedance measurements. The impedance sensor detects changes in acoustic coupling as the user moves the device away from the ear, and the system adapts the noise cancellation algorithm accordingly to maintain optimal performance across varying distances.
Solution Approach 2:
The system uses impedance measurement as feedback to monitor the distance between the speaker and user's ear. This feedback loop allows the adaptive noise cancellation processing to be continuously adjusted based on the actual acoustic coupling conditions, ensuring consistent performance regardless of device position.
2Measurement precision
If the user applies pressure between the device and ear, then the impedance increases providing distance information, but the acoustic radiation field is interfered with
Solution Approach 1:
The system replaces direct mechanical or optical distance measurement methods with electrical impedance measurement. By measuring the impedance changes caused by pressure application and distance variation, the system obtains precise distance information without requiring additional mechanical sensors or interfering with the acoustic radiation field directly.
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
Improves audio output quality by dynamically adjusting noise cancellation based on the user's ear position, maintaining effective noise reduction regardless of the distance between the speaker and the ear canal.
Implementation Method 1
An impedance of a speaker of a mobile device varies due to objects interfering with the speaker's acoustic radiation field. For example, when a user places the mobile device closer to the user's ear, the speaker impedance increases.
Implementation Method 2
an adaptive filter that processes an audio signal in accordance with a transfer function that models acoustic paths of the personal audio device, including an electro-acoustic path from the speaker to an error microphone
Data Source
AI summary
Coupling between a user's ear and a speaker of a mobile device may be determined by measuring an impedance of the speaker. When the user presses the mobile device against the user's ear, the speaker impedance changes as a result of loading in the speaker's acoustic radiation impedance. The speaker impedance change may be correlated with the force applied by the user to the mobile device. The measured speaker impedance may be provided as feedback to an adaptive noise cancellation (ANC) algorithm to adjust the output at the speaker. For example, when the mobile device is removed from the user's ear, the ANC algorithm may be muted.