THE IMPORTANCE OF ACOUSTICS
Acoustics encompasses the realm of sound transmission through solids and fluids. Sound may be described as the passage of pressure fluctuations through an elastic medium as the result of a vibrational impetus imparted to that medium. Acoustics has been the subject of many years of study, dating as far back as prehistoric times when ancient archers discovered their bowstrings made pleasant sounds, shepherds fashioned rudimentary flutes from reeds and music gradually evolved as an expression of human emotions. The ancient Chinese, Hindus, and Greeks began to study acoustics (the word itself is of Greek origin) on a mathematical basis. After a period of intellectual dormancy that characterized the Middle Ages, the evolution of acoustics as a science recommenced, with major contributions by Galileo, da Vinci, Newton, Laplace, Fermat, Huygens, Euler, the Bernoulli family, etc. The genesis of ultrasonics (i.e., the sound extending beyond human hearing at the high end of the frequency range). essentially occurred with the discovery of the piezoelectric effect by the Curie brothers, which provided the means of generating and detecting ultra high-frequency sounds.
While acoustics has originally aroused human interest through music, occurrence of echoes in valleys and glens and construction of amphitheaters,, modern acoustics is vastly different from the field that existed even twenty years ago. It has grown to encompass the realm of ultrasonics and infrasonics, as the result of applications in materials science, medicine. dentistry, oceanology, marine navigation, petroleum and mineral prospecting, industrial processes, and noise cancellation. Improvements are still being made in the older domains of music and voice reproduction, audiometry, psychoacoustics and environmental noise control.
Acoustics has already found wide applications in the biological sciences. Dental plaque is removed by ultrasonic means, sound waves are used to provide prenatal scans, new means of treating skin cancers have been devised through the use of high intensity ultrasonic signals, ultrasonic therapy is administered to athletes to treat soreness and muscular injuries and also to ease the effects of rheumatism, and sound in the appropriate ultrasonic range can break up kidney stones without the necessity for surgery. A device based upon the Doppler effect is used to indicate blood flow and motions of internal organs such as the heart and heart valves. Arguably the most ancient acoustic technique for diagnostic purposes is embodied in the stethoscope. With even more sophisticated instrumentation becoming available along with the advent of more powerful computer techniques, no doubt can remain that additional utilization of sound will be made for both diagnostic and therapeutic purposes.
1. Sir Francis Bacon (Lord Veralum), Sylva Sylvarum (published posthumously, 1626), The Works of Sir Francis Bacon, vol. 2, ed. J. Spedding, R. L. Ellis, and D. D. Heath, London: Longman and Co. et al., 1957.
2. Dale Emsinger, Ultrasonics, 2nd edition, New York: Marcel Dekker, Inc., 1988.
3. Frederick Vinton Hunt, Origins in Acoustics, Woodbury, NY: Acoustical Society of America, 1992.
4. Daniel R. Raichel, The Science and Applications of Acoustics, to be published, Springer Verlag, Heidelberg, 1999.
Move forward to anOVERVIEW OF ACOUSTICS AND ITS APPLICATIONS IN MEDICAL FIELDS
Support for the development of this module was provided by the National Science Foundation and The Cooper Union for the Advancement of Science and Art.
Please send questions or comments to Professor Ron Adrezin or Professor Daniel Raichel.