| 摘要 |
PURPOSE:To decrease number of echo cancellers and to reduce the circuit scale by arranging even number of microphones of same channel at an equal distance from the center of one channel speaker and providing number of differential amplifier circuits a half of which are of noninverting input type and remaining circuits of which are of an inverting input type. CONSTITUTION:L channel microphones 1A, 1B are arranged from a center of L channel speaker 6B of a same channel at an equal distance (d) so as to make the phase of a sound wave outputted by the L channel speaker 6B and that of a sound bypassed around the L channel microphones 1A, 1B the same, then the direct waves inputted in the same phase are cancelled by a differential amplifier 2A. Similarly, R channel microphones 1C, 1D are arranged from a center of R channel speaker 6A of a same channel at an equal distance (d) so as to make the phase of sound wave outputted by the R channel speaker 6A and that of a sound bypassed around the R channel microphones 1C, 1D the same, then the direct waves are cancelled by a differential amplifier circuit 2B. |
