CHAPTER X 



ULTRASONIC VIBRATIONS 



Earle C. Gregg, Jr., Case InslUule of Technology 



A . Fundamental Concepts 301 



1 . Frequency, Wavelength, and Amplitude 302 



2 . Pressure 304 



3 . Types of Sound Waves 304 



4 . Intensity 307 



5 . Reflection and Transmission at Boundaries 309 



6 . Absorption and Scattering 311 



7 . Cavitation and Degassing 312 



B . Production of Large Amplitude Ultrasound in Liquids 314 



1 . Magnetostriction Devices 314 



2 . Crystal Apparatus 318 



3 . Sound Field Measurements 326 



C . Biological Effects of Ultrasonic Vibrations 328 



1 . Lethal and SteriUzing Action 328 



2 . Thermal Effects 333 



3 . Chemical Effects of Ultrasonics and Secondary Results of 



Cavitation 335 



4 . Emulsification and Dispersion 336 



5 . Coagulation Effects 337 



6 . Natural Sources of Ultrasonic Sound 338 



7. Miscellaneous Applications of Ultrasonics 339 



References 340 



A. FUNDAMENTAL CONCEPTS 



The term "ultrasonics" is used in acoustics to denote those sound 

 frequencies that are bej^ond the up]>er frequency Hmit of the human 

 ear. Generally speaking, ultrasonic frequencies range from about 

 17,000 cycles per second upward, the upper Hmit being determined 

 solely by the equipment used. Recent investigations have produced 

 frequencies as high as 500,000 kilocycles per second. 



It is important to keep in mind that the laws of sound valid for 

 the audible range are also true for ultrasonics although in the latter 

 case other effects appear that had not been observed in the audible 



301 



