| 摘要 |
PROBLEM TO BE SOLVED: To obtain a height of projecting parts of fixed electrodes quantitatively, in a push/pull type electrostatic ultrasonic transducer. SOLUTION: In a push/pull type electrostatic ultrasonic transducer 1, a formula for optimally setting a height (t) of projecting parts of fixed electrodes 10A and 10B when a desired sound pressure and a driving frequency are given is formalized. The formula is obtained by a=(1/πf)√ä(I<SB>O</SB>*10<SP>P/10</SP>)/2ρ<SB>O</SB>c} when it is assumed that the desired sound pressure is P(dB), the driving frequency is f(Hz) and a value of one side amplitude of a film oscillation 12 is a(m), wherein Io denotes the reference acoustic intensity being 0.96×10<SP>-12</SP>(W/m<SP>2</SP>),ρo is the density of the air being 1.2(kg/m<SP>3</SP>), and (c) denotes the sound speed in the air being around 340(m/S). A value exceeding and closest to the one side amplitude value "a" obtained by the formula (at least in a range where an oscillation film never contacts with an electrode due to the film oscillation) is set to be the height (t) of the projecting parts of the fixed electrodes. COPYRIGHT: (C)2009,JPO&INPIT
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