Audio Gain Switching Circuit to Suppress Impulse and Step Noise
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Solution Overview
Problem
Existing signal processing apparatuses, such as amplifiers, generate stepwise noise during gain switching, and impulse-like noise when using a combination of analog and digital circuits, which cannot be effectively removed.
Innovation Solution
A signal processing apparatus comprising a first signal processing circuit and a second signal processing circuit, where the second circuit generates a second sound signal based on the first sound signal for a predetermined time after gain switching in the first circuit, using a sample hold portion and cross-fade portions to prevent impulse-like noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If gain switching is performed by a switch in an analog amplifier, then gain control is achieved, but impulse-like noise is generated in the output signal
Solution Approach 1:
A noise removal circuit is introduced as an intermediary component between the analog amplifier and the output. This circuit includes a subtraction unit that subtracts a noise signal (generated by switching a second amplifier's gain) from the output signal of the first amplifier, thereby removing impulse-like noise while preserving the desired audio output.
Solution Approach 2:
The invention utilizes the principle of parameter changes by switching the gain parameter of an amplifier. A second amplifier's gain is switched to generate a noise signal that mirrors the impulse-like noise produced by the first amplifier's gain switching. This noise signal is then subtracted from the output to cancel out the harmful noise components.
2Ease of operation
If gain switching is performed in an amplifier, then gain adjustment is achieved, but stepwise noise is generated in the output signal
Solution Approach 1:
The noise removal circuit acts as an intermediary that processes the output signal by subtracting the generated noise signal. This subtraction operation removes stepwise noise components while maintaining the legitimate audio signal, effectively cleaning the output without affecting the gain adjustment functionality.
3Adaptability or versatility
If a combination of analog and digital amplifiers is used, then signal processing capability is improved, but impulse-like noise cannot be removed and appears in the final output
Solution Approach 1:
The noise removal circuit serves as a mediator between the analog and digital signal processing stages. It captures the noise generated during gain switching in the analog amplifier and uses a second amplifier to generate a compensating noise signal that, when subtracted, removes the impulse-like noise from the final output while preserving the enhanced signal processing capabilities.
Data Source
AI summary
A signal processing apparatus includes a first signal processing circuit configured to generate a first sound signal based on an input signal, and a second signal processing circuit configured to generate a second sound signal based on the first sound signal. In a case that a gain of the first signal processing circuit is switched, the second signal processing circuit generates, for a predetermined time after the gain of the first signal processing circuit is switched, a value of the second sound signal based on a value of the first sound signal at or before a timing of the gain of the first signal processing circuit being switched.