Publisher's Synopsis
Sound detection is critical in the development of many systems such as meters or other sensing systems. These different disciplines require detailed understanding of the fundamentals of acoustics and ultrasonics. Sound is indispensable to humans as a media for communication among humans and natural world, and for cultural activities such as music. Also, with advancement of multimedia technology, opportunities for simultaneously using sound and video are increasing, leading to increasing importance of technology to handle sound. Recently, sound is used for various measurements and devices, not just having an aspect of being audible. Thus, acoustic science and acoustic engineering have a broad array of their applied areas with increasing importance. The concept of acoustic wave is a pervasive one, which emerges in any type of medium, from solids to plasmas, at length and time scales ranging from sub-micrometric layers in microdevices to seismic waves in the Sun's interior. This book presents several aspects of the active research ongoing in this field. The term sonic is applied to ultrasound waves of very high amplitudes. Ultrasound waves are longitudinal, compressional waves, that can be periodic or pulsed, propagate at roughly 1500 m/s in water or biological tissue, can leave the medium unchanged (diagnostic ultrasound), but at higher intensities can also change it (therapeutic ultrasound). Ultrasonic' therefore covers a huge range of frequencies from dogs hearing just above 20 kHz through a few MHz as used in ultrasound imaging to GHz used in acoustic microscopy. The general principle involved in generating ultrasonic waves is to cause some dense material to vibrate very rapidly. The vibrations produced by this material than cause air surrounding the material to begin vibrating with the same frequency. These vibrations then spread out in the form of ultrasonic waves. Ultrasonic waves are well-known for their broad range of applications. . Ultrasonic waves proved to be an excellent method for determining the depth of water. Ultrasonics also are used to map the shape of lake and ocean floors. Submarines use ultrasonic waves to maintain secret contact with each other. In industry, ultrasonic waves have been used in the testing of machinery and machine parts. Using a narrow beam of ultrasound, engineers can look inside metal parts in much the same way that doctors use X rays to examine the human body. With ultrasonic technology, flaws in machinery can be detected and repaired without having to take them apart. Similar ultrasonic methods have been used to diagnose problems in the human body. As an ultrasonic beam passes through the body, it encounters different types of tissue such as flesh, bone, and organs. Each type of tissue causes the ultrasonic beam to reflect in a different way. By studying these reflections, physicians can accurately map the interior of the body. Unlike X rays, there is no risk of harmful overexposure with ultrasonics. Therefore, they have become a useful alternative to X rays for diagnosis and are often used on sensitive organs, such as kidneys, as well as to monitor the progress of pregnancies. This book presents a number of state-of-the-art applications of ultrasonic waves, developed by the main researchers in their scientific fields from all around the world. Readers will find this book ta valuable source of information where authors describe their works in a clear way, basing them on relevant bibliographic references and actual challenges of their field of study.
