Two-Step Audio Muting Control for Low-Impedance Pop Noise Suppression
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Solution Overview
Problem
Existing audio signal muting circuits in audio equipment face challenges in instantaneously setting the volume to zero without increasing impedance, leading to potential pop noise during power-on or selector switching, and compromising sound quality in normal reproduction modes.
Innovation Solution
A muting control device with a volume control section and a muting circuit that allows for instantaneous switching to an attenuating state, followed by maximum attenuation by the volume control section, allowing for small impedance and reduced pop noise, while maintaining sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the resistance value of the muting circuit is increased to achieve complete attenuation of the audio signal, then the volume level is set to zero, but the impedance component increases causing deterioration in sound quality during normal reproduction mode
Solution Approach 1:
The patent divides the attenuation function into two separate circuits: a muting circuit with fixed resistance values that provides initial attenuation, and a volume control circuit that provides additional attenuation. This segmentation allows each circuit to use optimal resistance values - the muting circuit uses smaller resistance values to minimize impedance impact on sound quality, while the volume control circuit compensates to achieve the required total attenuation amount.
2Ease of operation
If electronic volume is used to control the audio signal to mute mode, then the volume level can be adjusted, but it cannot set the volume level to zero instantaneously requiring a certain time period
Solution Approach 1:
The patent applies preliminary action by having the muting circuit activate first to provide immediate attenuation when transitioning to mute mode. This initial attenuation action occurs before the volume control circuit completes its adjustment, ensuring that pop noise is suppressed instantly while the volume control circuit subsequently adjusts to achieve complete silence.
3Manufacturing precision
If a number of muting circuits are provided in series to increase the attenuation amount, then the volume level can be set to zero, but the impedance component increases causing deterioration in sound quality
Solution Approach 1:
The patent merges the attenuation function of the muting circuit with the volume control circuit. Instead of providing multiple muting circuits in series, the system combines the fixed attenuation of the muting circuit with the variable attenuation of the volume control circuit, achieving the required total attenuation with a single muting circuit and reducing overall system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables instantaneous muting with minimal impedance, effectively reducing pop noise during power-on or selector switching and maintaining sound quality by using a two-step attenuation process.
Implementation Method 1
The muting circuit is constituted from resistors inserted in series in an audio signal line and a transistor inserted between the audio signal line and the ground potential. In the attenuating state, attenuating the audio signal by a predetermined amount of attenuation
Implementation Method 2
volume control section capable of setting an amount of attenuation and controlling a volume level of the input audio signal
Data Source
AI summary
When controlling the audio signal to the mute mode from an unmute mode, first, the muting circuit switches from the non-attenuating state to the attenuating state to cause the muting circuit to attenuate the audio signal by the predetermined amount of attenuation, and then, the amount of attenuation by the volume control section is set to the maximum amount of attenuation to cause the volume control section to attenuate the audio signal by the maximum amount of attenuation.