Headset Voice Occlusion Compensation Using Transfer Function Equalization
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Solution Overview
Problem
Hearing devices cause passive loss of high-frequency sounds and amplification of low-frequency sounds due to ear occlusion, leading to a muffled and boomy voice for users, which existing feedback active noise cancellation methods fail to adequately address without preset parameters and phoneme-specific adjustments.
Innovation Solution
A method and apparatus using signal analysis and processing in headsets with internal and external microphones and processors to determine and equalize audio transfer functions, comparing closed-ear and open-ear conditions to restore natural voice quality by applying hearing augmentation equalization, both in the frequency and time domains, and adjusting for active noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If feedback active noise cancellation is used to compensate for occlusion effect, then low-frequency amplification is reduced, but high-frequency passive loss is not adequately addressed and the system complexity increases
Solution Approach 1:
The patent segments the occlusion effect compensation into two distinct components: high-frequency passive loss compensation and low-frequency occlusion effect compensation. This is achieved by implementing separate equalization filters - a high-frequency equalization filter for PL compensation and a feedback ANC filter for OE compensation - allowing each to be optimized independently rather than using a single unified approach
Solution Approach 2:
The patent introduces an intermediary classification mechanism that categorizes frequencies into high-frequency and low-frequency bands. This intermediary classification allows the system to apply different compensation strategies to different frequency ranges, with high-frequency signals processed through one path and low-frequency signals through another, thereby resolving the contradiction between addressing both frequency regions and maintaining system simplicity
2Object-affected harmful factors
If tightly sealing earbuds are used to isolate environmental noise, then noise isolation is improved, but passive loss at high frequency and amplification at low frequency occur
Solution Approach 1:
The patent converts the harmful occlusion effect into a beneficial measurement tool. By using the user's own voice as a reference signal and measuring how it is altered by the earbud occlusion, the system creates a transfer function that characterizes the occlusion effect. This measured transfer function is then used to drive compensation filters that restore natural sound, thereby converting the harmful occlusion into useful information for compensation
Solution Approach 2:
The patent dynamically changes the equalization parameters based on the measured transfer function characteristics. The high-frequency equalization filter applies gain adjustments at high frequencies to compensate for passive loss, while the feedback ANC filter applies opposite-phase signals at low frequencies to cancel occlusion effect. These parameter changes are adaptively determined by the transfer function measurement process
Data Source
AI summary
A method of equalising sound in a headset comprising an internal microphone configured to generate a first audio signal, an external microphone configured to generate a second audio signal, a speaker, and one or more processors coupled between the speaker, the external microphone, and the internal microphone, the method comprising: while the headset is worn by a user: determining a first audio transfer function between the first audio signal and the second audio signal in the presence of sound at the external microphone; and determining a second audio transfer function between a speaker input signal and the first audio signal with the speaker being driven by the speaker input signal; determining an electrical transfer function of the one or more processors; determining a closed-ear transfer function based on the first audio transfer function, the second audio transfer function and the electrical transfer function; and equalising the first audio signal based on a comparison between the closed-ear transfer function and an open-ear transfer function to generate an equalised first audio signal.