| 摘要 |
PURPOSE:To perform comfortable duplex transmission and reception by holding a couple of oscillating pickup elements which have nearly equal characteristics at distance in parallel to an earplug axis in such a way that their maximum sensivity directions are coincident with each other. CONSTITUTION:At a rearwise position in a earplug 1, a holding member 6 is fixed to hold a couple of oscillating pickup elements 7 and 8. Those elements 7 and 8 are so adjusted that their characterisitcs are nearly equal while held at distance in such a way that their maximum sensivity directions are coincident with each other without any mutual influence. At the center part between these elements 7 and 8, a sound path pipe 22 is fixed in the axis direction of the earplug 1 and a sound passage 24 is formed in the pipe 22. In this constitution, when oscillation is conducted to the elements 7 and 8, outputs having equal amplitude appears at output terminals 11 and 12, and 13 and 14 of the elements 7 and 8. Sound pressure from a handset 23, on the other hand, is listened through a conduction path 24, but the unnecessary outputs are in the opposite direction to the elements 7 and 8, so that they are balanced and canceled. |
