Audio Dynamic Range Control Using Instant Amplitude Compression
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Solution Overview
Problem
Existing hearing aid systems suffer from audible gaps and pumping issues due to imperfect adjustment of time constants, which affect the intelligibility of spoken words, and lack an automatic solution to minimize these problems.
Innovation Solution
The process utilizes an instant amplitude signal A(t) for real-time control of nonlinear amplification, allowing for delay-free processing without increasing pumping probability, and combines it with adjustable linear amplification to enhance intelligibility, using a combination of Hilbert signals and adjustable threshold amplitudes to define amplification characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compression of audio signal is performed using conventional methods with time constants, then amplification of low amplitudes is improved, but audible gaps and pumping effects occur
Solution Approach 1:
The patent changes the fundamental parameter used for compression control from time-based constants to instant amplitude A(t). This parameter change allows the system to respond immediately to signal amplitude changes without the delay and smoothing effects of conventional time constants, thereby eliminating audible gaps and pumping while maintaining intelligibility improvement.
Solution Approach 2:
The patent replaces the mechanical/time-based control system (using attack and release time constants) with an instantaneous amplitude-based control system. The Hilbert transform methodology substitutes the conventional temporal smoothing approach with a mathematical transformation that provides instant amplitude information, eliminating the need for time constant adjustment and preventing pumping effects.
2Speed
If delay-free processing is used to prevent audible gaps, then response time is improved, but pumping probability increases
Solution Approach 1:
The patent changes the control parameter from time constants to instant amplitude A(t), which provides immediate response without delay while avoiding pumping. The instant amplitude, derived through Hilbert transform, captures the instantaneous energy of the signal without requiring temporal smoothing, thus achieving both fast response and pumping prevention.
3Object-affected harmful factors
If manual adjustment of time constants is performed to reduce pumping, then pumping effects are decreased, but adjustment complexity and lack of automation increase
Solution Approach 1:
The patent implements self-service by using the instant amplitude A(t) to automatically control the nonlinear amplification without requiring manual adjustment of time constants. The system adapts in real-time to the input signal characteristics, eliminating the need for user intervention or complex adjustment procedures while preventing pumping effects.
Solution Approach 2:
The patent employs feedback through the instant amplitude A(t) which continuously monitors the signal and automatically adjusts the compression behavior. This closed-loop control using instantaneous amplitude information eliminates the need for manual time constant adjustment and prevents pumping without adding user-facing complexity.
4Reliability
If nonlinear amplification is applied to enhance low amplitude signals, then intelligibility is improved, but audible gaps and pumping occur due to imperfect adjustment
Solution Approach 1:
The patent changes the control parameter from time constants to instant amplitude A(t) to control nonlinear amplification. This parameter change enables precise, real-time control of compression behavior that adapts to signal characteristics without causing audible gaps or pumping, while maintaining the intelligibility benefits of enhanced low amplitude signals.
Data Source
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AI summary
The invention relates to a process for modifying an input signal, preferably an audio signal, comprising the splitting of the input signal into at least a first input part and a second input part, the amplification of at least the first input part with a linear gain to create a first output part and the nonlinear amplification of at least the second input part of the input signal to create a second output part and summing the first output part and the second output part in order to provide an output signal. To decrease the probability of pumping and audible gaps and enhance the intelligibility of spoken words, for the nonlinear amplification an instant amplitude signal correlated to the second input part is generated and used for controlling the nonlinear amplification and the instant amplitude signal is generated by producing an analytical signal consisting of two Hilbert-signals with the same energy spectrum as the second input part and calculating the square root of the sum of the squares of the Hilbert signals.