| 摘要 |
PURPOSE:To reduce production of a beat sound noise by forming a recessed part for suppressing beat noise to a major face at the outside of a flange of a drum magnetic core so as to avoid delivery of vibration of a drum magnetic core due to magnetostriction. CONSTITUTION:A ferrite-made (for example) drum magnetic core 1 having flanges 2, 2 and a cylindrical magnet made of, e.g. ferrite and a resin made base 4 with lead terminals 5, 5 planted to a lower face are provided to both ends of a pillar and ends of winding 6 wound on the pillar of the magnetic core 1 are wound to roots of the lead terminals 5, 5 and soldered. Then a recessed part 7 of a truncated cone is formed in the middle of the major face at the outside of the upper lower flanges 2, 2 of the drum magnetic core 1. Thus, the vibration of the magnetic core 1 is shut at the recessed part 7 to suppress the delivery to an insulation base 4 and the magnet 3 fixed to the upper and lower flanges 2, 2, resulting that production of beat sound noise unpleasant in a listening sense is reduced. |
