ANR Headphones Acceleration Sensor Occlusion Effect Compensation
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Solution Overview
Problem
Active noise reduction (ANR) headphones fail to effectively counteract the occlusion effect, which causes unnatural amplification of low frequencies and self-generated sounds due to increased acoustic impedance, especially during physical activities.
Innovation Solution
The implementation of ANR headphones equipped with a loudspeaker, external and internal microphones, and an acceleration sensor, using a controller to generate a composite compensation signal that combines ambient noise, residual noise, and acceleration signals through feed-forward and feedback filters to compensate for the occlusion effect, with optional adaptive filter coefficients based on the Wiener-Hopf equation and Filtered-x Least Mean Square algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If acoustically closed headphones are used to achieve good attenuation of outside ambient noise, then audio reproduction quality is improved, but the occlusion effect occurs causing unnatural amplification of low frequencies and self-generated sounds
Solution Approach 1:
The patent employs a feedback control mechanism where an internal microphone detects the residual noise signal within the ear canal, and the controller generates a compensation signal based on this detection to counteract the occlusion effect. This closed-loop feedback system dynamically adjusts the compensation based on actual conditions inside the ear canal.
Solution Approach 2:
The patent introduces an acceleration sensor as an intermediary device that detects physical activities of the user and generates an acceleration signal. This intermediary sensor provides additional information about user movement that helps the controller generate more accurate compensation signals for the occlusion effect caused by physical activities.
2Object-generated harmful factors
If active noise reduction schemes are used to counteract the occlusion effect, then low-frequency amplification is reduced, but device complexity increases due to additional sensors and processing
Solution Approach 1:
The controller performs multiple functions: it processes ambient noise signals from the external microphone, residual noise signals from the internal microphone, and acceleration signals from the acceleration sensor. By combining these multiple input signals into a single composite compensation signal, the controller achieves multi-functionality without requiring separate processing systems for each function.
Solution Approach 2:
The patent merges multiple compensation signals (ambient noise compensation signal, residual noise compensation signal, and acceleration compensation signal) into a single composite compensation signal that drives the loudspeaker. This combining approach integrates multiple control functions into one unified system, reducing overall complexity compared to implementing separate systems for each compensation type.
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
Effectively reduces the occlusion effect by compensating for low-frequency amplification and noise disturbances during physical activities, ensuring improved audio reproduction quality and user experience.
Implementation Method 1
an acceleration sensor configured to generate an acceleration signal indicative of one or more accelerations experienced by the ANR headphones
Implementation Method 2
an external microphone (also referred to as reference microphone) configured to detect an ambient noise signal
Implementation Method 3
an internal microphone (also referred to as error microphone) configured to detect a residual noise signal. The residual noise signal may be detected within the ear canal of the user
Implementation Method 4
a loudspeaker configured to be driven by a loudspeaker signal for generating the sound signal
Data Source
AI summary
ANR headphones generate a sound signal, and include a loudspeaker, an external microphone configured to detect an ambient noise signal, and an internal microphone configured to detect a residual noise signal within an ear canal of the user. Moreover, the ANR headphones have an acceleration sensor configured to generate an acceleration signal indicative of accelerations experienced by the ANR headphones. A controller of the ANR headphones is configured to generate a loudspeaker signal based on a composite compensation signal. The composite compensation signal is a combination of an ambient noise compensation signal based on the ambient noise signal, a residual noise compensation signal based on the residual noise signal and an acceleration compensation signal based on the acceleration signal.