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The sounds that humans can hear are limited to the audible range of frequencies , between twenty and twenty thousand hertz. Within this range, higher frequencies are heard as higher pitched, and lower frequencies are heard as lower pitched. Anything above the audible range is considered ultrasonic, and any sound that falls below it is called infrasound. Some animals use ultrasound to navigate their environment, a technique known as "echolocation." The principle behind echolocation is one that... więcej
Salem Press Encyclopedia of Science, 2023. 3p.
Although ultrasound cannot be heard by humans, it has been produced and used for a vast number of applications in many different fields. In industry, ultrasound has been used as a technique to assess the structural integrity of materials. The interaction between ultrasound and live systems has been studied since the 1920s. During the 1960s, it was used in medicine, initially as a therapeutic option and then later as a diagnostic resource. In the twenty-first century, ultrasound is a major... więcej
Salem Press Encyclopedia of Science, 2022. 2p.
Ultrasound works on a principle similar to that of radar, which transmits then receives radio waves and converts them into an image. Structures within the body are differentiated by the varying degrees that they reflect a focused sound beam. Ultrasound is one of the most widely used diagnostic medical tools.
Salem Press Encyclopedia of Science, 2022. 3p.
In the early 1900’s, two major events made it essential to develop an appropriate means for detecting unseen underwater objects. First, the Titanic disaster in 1912 involved a large submerged, unseen, and silent iceberg. This obstructive and destructive iceberg caused the sinking of the Titanic and resulted in the loss of many lives and of valuable treasure. The second event was the threat to the Allied powers by German U-boats during World War I. The threat of possible defeat at sea was... więcej
Salem Press Encyclopedia, 2023. 3p.
