Here, we propose functional earphone using magnetostrictive vibrator

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Development of Functional Earphone using Magnetostrictive Material

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Toshiyuki UENO (Mem.), Hidemitsu MIURA, Sotoshi YAMADA (Mem.)

In daily life, we often use earphone to listen sound and music. However kanal type earphone like earplug shape shuts off the sound of surroundings, thus, is not preferable to use in jogging or driving. Bone conductive speaker is alternative to hear sound from surroundings and player simultaneously. However conventional ones based on piezoelectric material or voice coil are large size, difficult to equip, and amplifier necessary due to the low output force. Here, we propose functional earphone using magnetostrictive vibrator. The device consists of magnetostrictive rod (Galfenol) and magnetic yoke constructing unimorph structure, winding coil, bias magnet and vibration plate. The ring shape vibrator with hole to pass air-conductive sound is easy to equip on ear hole and can generate sufficient sound without additional amplifier. In this study, we fabricate several prototypes to evaluate static and dynamic characteristics to verify the principle and advantages.

Keywords: magnetostrictive material, Galfenol, cylindrical, earphone, bending vibrator.

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Fig. 2 Principle, bias (left) and exited (right).

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Fig. 4 Measurement setup.

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Fig. 6 Comparison of displacement vs. current.

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Fig. 8 Evaluation method.

Fig. 9 Comparison of minimum voltage to percept sound by mounting methods.

Fig. 10 Vibration acceleration vs. frequency.

Fig. 11 Comparison of minimum voltage to percept sound by structure.

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Fig. 12 Canal type bone conductive earphone.

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[1] ��

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[2] ��

��NEC TOKIN Technical Review, Vol. 32, 2005.

[3] A. E. Clark, M. Wun-Fogle, and J. B. Restorff, Magnetostrictive Properties of Body-Centered Cubic Fe-Ga and Fe-Ga-Al Alloy, IEEE Trans. Magn., Vol. 37, pp. 3238-3240, 2000.

[4] T. Ueno, T. Higuchi, E. Summers, M. Wun-Fogle, Micro-magnetostrictive vibrator using iron-gallium alloy, Sensors and Actuators A, Vol. 148, pp. 280-284, 2008.

[5] A. E. Clark, M. Wun-Fogle, J. B. Restorff, Magnetostrictive property of Galfenol alloys under compressive stress, Mater.

Trans., Vol. 43, pp. 881-886, 2002.

[6] ��

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Vol. 105, pp. 19-24, 2005.

Here, we propose functional earphone using magnetostrictive vibrator

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