Signal Processing Apparatus Suppressing System Sound for Echo Cancellation
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Solution Overview
Problem
Conventional echo cancellation technologies fail to fully cancel system sounds, such as ringback tones, when the volume of the over-the-phone sound is high, leading to incomplete cancellation and potential incorrect detection during handsfree communication.
Innovation Solution
A signal processing apparatus that generates an output sound signal by combining over-the-phone and system sound signals, suppresses the level of the system sound signal to prevent it from exceeding a predetermined value, and uses an echo canceller to ensure complete cancellation of the system sound from the input sound signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the volume of the over-the-phone sound signal is increased, then the clarity of the over-the-phone communication is improved, but the system sound cannot be fully cancelled by the echo cancellation circuit
Solution Approach 1:
The patent applies preliminary action by suppressing the level of the system sound signal before it is combined with the over-the-phone sound signal and output to the loudspeaker. The output controller reduces the system sound level to a predetermined value or lower in advance, ensuring that when the sounds are combined, the echo cancellation circuit can successfully cancel the system sound from the microphone input regardless of the over-the-phone sound volume level.
2Illumination intensity
If the level of the system sound signal is increased, then the audibility of the system sound (e.g., dial tone) is improved, but the echo cancellation fails to remove it completely
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the level parameter of the system sound signal based on the volume setting of the over-the-phone sound. The output controller changes the system sound level parameter to be equal to or lower than a predetermined value, ensuring that the combined output signal remains within the effective cancellation range of the echo cancellation circuit while maintaining adequate audibility.
Data Source
AI summary
A signal processing apparatus includes a generator, an output controller, and an echo canceller. The generator generates an output sound signal by combining an over-the-phone sound signal with a system sound signal different from the over-the-phone sound signal. The output controller outputs, to a loudspeaker, the output sound signal generated by the generator. The echo canceller cancels the output sound signal from an input sound signal input via a microphone located in a vicinity of the loudspeaker. The output controller suppresses a level of the system sound signal to be output from the loudspeaker so as not to be greater than a predetermined value within a range in which a volume value for the over-the-phone sound signal is settable.