Hands-free Telephone Loudspeaker Selection Echo Reduction
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Solution Overview
Problem
Conventional hands-free telephone conversation apparatuses suffer from echo cancellation methods that deteriorate the sound quality by adding echo cancellation signals to sound signals intended for far-end users.
Innovation Solution
The apparatus employs a loudspeaker selecting mechanism to output sound from a loudspeaker not directed towards the microphone, avoiding echo cancellation processing and using a band pass filter with dynamically set coefficients based on sound pressure levels to optimize sound transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If echo cancellation signal is added to sound signal to be transmitted to far-end user, then echo is cancelled, but sound quality is deteriorated
Solution Approach 1:
The patent extracts and removes the problematic component (loudspeaker directed at microphone) from the system configuration. By selecting a loudspeaker that is not directed toward the microphone, the system eliminates the echo path at its source, avoiding the need for echo cancellation processing that degrades sound quality.
Solution Approach 2:
The patent introduces a loudspeaker selecting mechanism as an intermediary component that mediates between the sound signal source and the microphone. This selector chooses the optimal loudspeaker configuration (one not directed at the microphone) to prevent echo while maintaining sound quality.
2Power
If loudspeaker directed toward microphone is used, then sound output is strong, but echo is generated
Solution Approach 1:
The patent applies local quality by creating different spatial zones for sound output. The loudspeaker not directed toward the microphone provides sufficient sound output in the desired direction while creating a quiet zone toward the microphone, thereby preventing echo generation.
Solution Approach 2:
The patent utilizes asymmetric positioning and orientation of the loudspeaker relative to the microphone. Instead of symmetric or directly facing configuration, the loudspeaker is positioned and directed asymmetrically (not toward the microphone) to achieve sound output while minimizing echo feedback.
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
This approach effectively reduces echo influence on sound quality for far-end users without degrading the sound, enhancing clarity and reducing echo-related distortions.
Implementation Method 1
a band pass filter for filtering sound signals received from the loudspeaker
Implementation Method 2
sound pressure level detecting means for detecting a sound pressure level of a test sound from a loudspeaker selected by the loudspeaker switching means
Data Source
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AI summary
It is an object of the present invention to provide a hands-free telephone conversation apparatus which can reduce negative influence of an echo on a sound to be transmitted to a far-end user without deteriorating the sound. When a MPU determines that a mobile phone receives an incoming call (in step S1), and a user starts to talk on the mobile phone, in accordance with an operation of an input device connected to an in-vehicle bus line, a MPU controls the mobile phone to have the mobile phone output, to the DSP, a sound signal indicative of a sound to be transmitted to the far-end user, and to have a switch select a loudspeaker, installed in an vehicle without being directed to the microphone, as a loudspeaker for outputting a sound received from the far-end user (in step S5).