Transient Suppression Circuit for Hearing Aids
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Solution Overview
Problem
Hearing aid wearers often find transient sounds, such as those from slamming doors or dropping objects, unpleasant and annoying, despite these sounds not being loud enough to trigger output compression, highlighting a need to reduce their harshness without affecting intended sounds like speech and music.
Innovation Solution
An audio system with a transient suppression circuit that rectifies input signals, generates a threshold envelope, accumulates and normalizes the difference between the rectified signal and the threshold, and applies a calculated gain to suppress transient sounds, maintaining the intended sounds' integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If output compression limiting is applied to reduce transient sounds, then transient sound harshness is reduced, but intended sounds like speech and music are also affected and distorted
Solution Approach 1:
The patent applies different processing characteristics to different portions of the audio signal by detecting transient characteristics (rapid amplitude changes) and applying suppression only to those portions while leaving steady-state sounds unchanged. This localized approach reduces transient harshness without affecting speech and music quality.
Solution Approach 2:
The system dynamically adjusts the suppression threshold and gain reduction based on the instantaneous characteristics of the input signal. By continuously monitoring signal amplitude and rate of change, the system adapts its response to preserve intended sounds while suppressing transients, rather than applying fixed compression parameters.
2Object-affected harmful factors
If strong compression is applied to suppress transient sounds, then transient harshness is reduced, but the overall volume and clarity of intended sounds are reduced
Solution Approach 1:
The patent implements selective suppression by identifying transient portions of the signal through detection of rapid amplitude changes and applying gain reduction only to those specific portions. The majority of the audio signal that constitutes speech and music remains at full amplitude, preserving overall volume and clarity.
Solution Approach 2:
The system applies periodic detection and suppression in response to transient events rather than continuous compression. The compression is activated only during transient occurrences and released immediately afterward, maintaining overall signal amplitude while selectively reducing unpleasant transient peaks.
Data Source
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AI summary
An audio system includes a transient suppression circuit that rectifies an input signal representing target sounds and transient sounds and produces a threshold envelope of the rectified input signal. The transient suppression circuit accumulates the difference between the rectified input signal and the threshold envelope, and normalizes the accumulated difference using the rectified input signal. A gain is calculated using this normalized accumulated difference and applied to the input signal to suppress the transient sounds without substantially affecting the target sounds.