| 摘要 |
<p>PURPOSE:To reduce external noise such as touch noise, by making the impedance for noise reduction smaller than the receiving unit impedance and by connecting outputs with phases opposite to each other. CONSTITUTION:Unit 8 for noise reduction which is so constituted that only the external vibration noise signal can be input is incorporated besides unit 7 for sound receiving, and outputs of units 8 and 7 are connected with phases opposite to each other in series. By this constitution, when mechaical external vibration is applied to hausing 5, diaphragms 10 and 14 of units 7 and 8 try to move in the same direction due to inertia. At this instant, electromotive force is generated in voice coils 11 and 15, and outputs of electromotive force of units 7 and 8 are connected in phases opposite to each other to cancel electromotive force of units 7 and 8, and the impedance of unit 8 is made smaller than the impedance of unit 7. As a result, external noise such as touch noise can be reduced.</p> |
