Noise barriers line approximately 1400 miles of U.S. Federal highways alone, with the number growing by 90 - 100 miles every year. Ultrasound techniques use high-pitched sound waves and their reflections to image the inside of the body, break up kidney stones, and stop internal bleeding. Sound waves can create high-energy bubbles in liquids. Intense heat and quick cooling of these bubbles speeds up chemical reactions for synthesizing pharmaceuticals. To obtain the best possible audio environment, new concert halls are designed with moveable canopies, curtains, and chambers that can be individually positioned to enhance the unique sound of each presentation.
Sound waves can identify defects in airplanes, bridges, and pipelines.
1900s - Magnetostrictive and piezoelectric devices are used to produce ultrasound at controllable frequencies. Submarine detection becomes possible. 1958 - J. MacVickar, I. Donald, and T.G. Brown use ultrasound to examine a fetus. Ray tracing and other sophisticated signal processing techniques are put into wide use. 1975 - Widespread use of ultrasound to image fetus, kidneys, brain and other internal organs.