Hearing Device Analog Preprocessing for Wind Noise Reduction
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Solution Overview
Problem
Existing hearing devices face challenges in effectively reducing wind noise, which degrades user experience and signal-to-noise ratio (SNR), often requiring digital filtering that can compromise normal sound processing.
Innovation Solution
A hearing device with a preprocessing unit that applies different transfer functions based on noise criteria, including a first and second cutoff frequency, to the audio signal, reducing A/D converter saturation and improving SNR by removing unwanted noise early in the signal processing stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If digital filtering is applied to reduce wind noise, then wind noise reduction is improved, but normal sound processing is compromised
Solution Approach 1:
The patent applies preliminary action by performing analog filtering in the preprocessing unit before the A/D converter. This early-stage filtering removes wind noise and other unwanted signals from the analog audio signal before it is digitized, preventing saturation of the A/D converter and preserving normal sound processing in the digital domain.
Solution Approach 2:
The preprocessing unit acts as an intermediary between the microphone and the A/D converter. It introduces an analog filtering stage that mediates the signal before digitization, removing harmful wind noise components while preserving the integrity of normal sound signals for subsequent digital processing.
2Object-affected harmful factors
If preamplifier gain is reduced to remove uncomfortable sound levels, then wind noise reduction is improved, but sound processing quality is destroyed
Solution Approach 1:
The patent applies local quality by implementing frequency-selective filtering in the preprocessing unit. Instead of uniformly reducing preamplifier gain across all frequencies, the analog filter selectively attenuates specific frequency ranges associated with wind noise while preserving the quality of normal sound frequencies for subsequent digital processing.
Solution Approach 2:
The patent changes the parameter of signal processing stage by moving filtering operations from the digital domain to the analog domain before A/D conversion. This parameter change allows for effective wind noise reduction without compromising the quality of sound processing, as the filter operates on the analog signal characteristics.
3Reliability
If analog filtering is applied in preprocessing unit, then A/D converter saturation is reduced, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the signal processing function into distinct stages: an analog preprocessing unit with filtering capability, followed by an A/D converter, and then digital processing. This segmentation isolates the analog filtering function to protect the A/D converter from saturation, while keeping each unit's complexity manageable and well-defined.
Data Source
AI summary
A hearing device includes: a microphone for converting audio into an audio signal; a preprocessing unit for analog processing of the audio signal and having an input and an output, wherein the input is connected to an output of the microphone; an A/D converter for converting the processed analog audio signal into a digital audio signal, the A/D converter having an input and an output, wherein the input of the A/D converter is connected to the output of the preprocessing unit; and a processing unit for digital processing of an output from the A/D converter, wherein the processing unit is connected to the preprocessing unit, and is configured to apply a first transfer function to the audio signal in a first mode of operation, or a second transfer function with a cutoff frequency to the audio signal in a second mode of operation, depending on a control signal.