Active Occlusion Cancellation in Hearing Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional hearing devices face challenges in reducing the occlusion effect, particularly when open fits are not feasible, due to gain or output power limitations, or when the ear canal must be sealed for protective purposes, as existing solutions like larger vents or deep fitting may not adequately address the issue of low frequency amplification.
Innovation Solution
A hearing device incorporating an active occlusion cancellation circuit with a combination of filters and subtractors that process audio signals to cancel undesired frequencies, utilizing a recursive filter and an adaptive filter to model the signal path from the receiver to the ear canal microphone, allowing for effective occlusion cancellation while maintaining dynamic range and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional solutions (larger vents, deep fitting) are used to reduce occlusion effect, then the occlusion effect is reduced, but device complexity increases and may not adequately address low frequency amplification
Solution Approach 1:
The patent replaces mechanical solutions (larger vents, deep fitting) with an active electronic system consisting of microphones, signal processors, and speakers that generate anti-phase sound waves to cancel the occlusion effect through destructive interference, thereby reducing low frequency amplification without increasing mechanical complexity
Solution Approach 2:
The system uses microphones to detect sound pressure in the ear canal, processes this feedback signal through adaptive filters to model the transfer function, and adjusts the anti-phase signal accordingly to continuously cancel the occlusion effect dynamically
2Object-affected harmful factors
If active occlusion cancellation is implemented, then occlusion effect is reduced, but device complexity and computational requirements increase
Solution Approach 1:
The signal processing is divided into distinct functional modules: detection microphones, adaptive filtering stage for transfer function modeling, subtraction stage for generating anti-phase signals, and output speakers, allowing independent optimization and implementation of each component
Solution Approach 2:
The system performs preliminary characterization of the ear canal acoustics by measuring the transfer function between speakers and microphones during an initialization phase, storing this model for subsequent real-time occlusion cancellation without requiring continuous complex computations
3Reliability
If the ear canal is sealed for protective purposes, then protection is provided, but occlusion effect increases with low frequency amplification up to 30 dB
Solution Approach 1:
The system converts the harmful occlusion effect caused by ear canal sealing into a beneficial cancellation mechanism by using the same sealed environment to contain and control the anti-phase sound waves, allowing the seal to serve both protective and active cancellation functions simultaneously
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 solution effectively reduces the occlusion effect by minimizing the perception of body-conducted sound, maintaining dynamic range, and adapting to changes in the signal path, thus providing improved sound quality and user experience.
Implementation Method 1
a first filter having an input that is connected for reception of the second combined audio signal for provision of a filtered second combined audio signal to the second input of the first subtractor, and a second filter having an input that is connected for reception of the processed audio signal generated by the signal processor
Implementation Method 2
a first subtractor having a first input that is connected for reception of the processed audio signal and a second input and an output for provision of a first combined audio signal that is equal to the signal received at the first input minus the signal received at the second input of the first subtractor
Implementation Method 3
a receiver connected for reception of the first combined signal for converting the combined audio signal into an output sound signal for emission towards an eardrum of a user
Data Source
AI summary
A hearing device includes: a microphone for providing an audio signal; a signal processor for generating a processed audio signal; a first subtractor having a first input for receiving the processed audio signal, a second input, and an output for providing a first combined audio signal; a receiver for converting the first combined audio signal into an output sound signal; an ear canal microphone configured to provide an ear canal audio signal; a second subtractor having a first input for receiving the ear canal audio signal, a second input, and an output for providing a second combined audio signal; a first filter for receiving the second combined audio signal and for providing a filtered second combined audio signal to the second input of the first subtractor; and a second filter for providing a filtered processed audio signal to the second input of the second subtractor.