Speakerphone Transmit Gain Control for Stable Hands-Free Voice Levels
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Solution Overview
Problem
Fluctuations in mouth position relative to the speakerphone can significantly impact transmit signal levels, degrading voice signal quality and requiring increased listening attention from the recipient, especially in hands-free speakerphone mode.
Innovation Solution
Implementing automatic gain control (AGC) in the speakerphone's transmission system to measure and adjust the send output level of the audio signal based on a threshold value, ensuring consistent voice transmission by comparing the send output level with a predetermined threshold and applying gain as necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If speakerphone mode is used for hands-free operation, then ease of operation is improved, but transmit signal level stability deteriorates due to mouth position changes
Solution Approach 1:
The patent implements automatic gain control (AGC) that continuously monitors the transmit signal level and dynamically adjusts the gain to compensate for mouth position changes. The system measures the actual transmit level and feeds this information back to the AGC circuit, which automatically adjusts amplification to maintain stable signal levels despite variations in user positioning.
Solution Approach 2:
The patent changes the gain parameter dynamically based on detected signal level conditions. The AGC system adjusts the amplification factor in real-time according to the measured transmit level, transforming a static gain setting into a dynamic parameter that adapts to changing mouth positions and signal conditions.
2Reliability
If automatic gain control is implemented to stabilize transmit volume, then voice signal quality is improved, but device complexity increases
Solution Approach 1:
The AGC system is self-regulating and requires no manual intervention. It automatically detects signal level deviations and adjusts gain without user input, making the system self-correcting. The transmission system monitors and adjusts itself, eliminating the need for external control mechanisms.
Solution Approach 2:
The AGC circuit serves multiple functions: it stabilizes transmit signal levels, compensates for mouth position variations, and maintains consistent audio quality across different operating conditions. This single component addresses multiple signal quality issues that would otherwise require separate correction mechanisms.
Data Source
AI summary
A method and apparatus for controlling the transmit volume level of a speakerphone includes receiving a transmit audio signal. If the speakerphone is in a speakerphone mode, the method further includes measuring a send output level of the transmit audio signal, comparing the send output level of the transmit audio signal with a send output level threshold value, and controlling the send output level of the transmit audio signal based upon the comparison of the send output level of the transmit audio signal and the send output level threshold value using automatic gain control. Some embodiments further include determining the send output level threshold value based upon a send loudness rating (SLR) target difference value between a speakerphone SLR target value and a handset SLR target value. In some embodiments, if the speakerphone is in a handset mode, the send output level of the transmit audio signal remains substantially the same.