| 摘要 |
PROBLEM TO BE SOLVED: To improve a signal/noise ratio at hands-free call by reducing sound coupling. SOLUTION: A sound coupling characteristics from a speaker 51 to a microphone 56 is studied. For that purpose, an impulse response is acquired at an ANC61 before a call. During a call, a pseudo echo signal is generated using a transfer function acquired from the impulse response. An analogue adder 36 is used for addition in opposite phase to the signal from the microphone 56, resulting in reduced sound coupling. The ANC61 is easily operated using an LMS algorism. At measuring the sound coupling characteristics, coupling with direct sound along a device case, coupling with sound through the interior of the case, as well as coupling with case vibration are used.
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