ULTRASONICS AND HYPERSONICS. A REVIEW.
Abstract
Ultrasonics has been defined as the science of sound waves above the audible (i.e. above 20 KHZ). Such waves have a variety of analytical uses and engineering applications. Low amplitude applications are sonar systems, delay lines, mechanical filters, ultrasonic inspectoscopes, thickness gages and ultrasonic imaging. High amplitude ultrasonics have been used in cleaning (by cavitation) machining and welding, aglomeration of particles and medical therapy. Analytical uses are in investigating relaxation in gases, liquids and solids, domain wall motions in magnetic materials and in low temperature effects in liquid helium and in superconductors. Hypersonics is the extension of ultrasonics to frequencies from 500 MHZ to the limiting frequencies transmitted by liquids and solids. The methods used are acoustic pulse transmission, Brillouin scattering and thermal pulse methods. The last method has shown that in insulators thermal motions arrive as sound pulses a finite time after initiation. In metals the arrival time is determined by the Fermi velocity of the electrons. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1968
- Accession Number
- AD0667735
Entities
People
- W. P. Mason
Organizations
- Columbia University