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Nebulizers designed to provide an aerosol mist by means of ultrasonic frequency oscillations. These nebulizers typically consist of an electronic oscillator, an ultrasound transducer (piezoelectric crystal), a coupling basin, a nebulizer chamber, and a fan. A high-frequency (typically 1-2 MHz) electrical current is applied to a piezoelectric crystal within the oscillator circuit, which changes the applied electrical signal into mechanical vibrations. These vibrations, in turn, produce 1-2 MHz sound waves in the coupling basin. The coupler (water or saline) transmits the sound waves to the (medicated) solution in the nebulizer chamber. When the sound waves reach the fluid-air interface, the fluid forms a geyser and disperses into a fine-particle aerosol mist. The size of the mist particles is determined primarily by the vibrating frequency; the higher the frequency the smaller the particles. Ultrasonic nebulizers produce particles in the size range of 0.5 to 35 micrometers.
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