| 摘要 |
PROBLEM TO BE SOLVED: To configure a precise sound field control device, a noise control device, a hands-free phone and an acoustic reflection plate by adopting a bidirectional transmission amplifying system of an electromagnetic type electroacoustic system two-way conversion element configuring a loudspeaker or an earphone. SOLUTION: A current output type power amplifier is employed for the power amplifier of an electric system and the electrical characteristics of the conversion element from the standpoint of an electrical side of the electroacoustic system is measured precisely in advance or continuously during operation, so as to extract a signal of an acoustoelectric system from a difference between a virtual electromotive force and real electromotive force.
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