ultrasonen

Ultrasonen, commonly referred to as ultrasound, are sound waves with frequencies above the human hearing range, typically above 20 kilohertz. They propagate through air, liquids, and solids, and their speed and attenuation depend on the medium. In air the speed is about 343 m/s at room temperature; in water and solids it is higher. Higher frequencies yield better resolution but shorter penetration due to attenuation.

Generation and detection: Ultrasonen are mainly produced by piezoelectric transducers, sometimes magnetostrictive devices. A transducer converts electrical signals into mechanical vibrations to emit waves; echoes returned from interfaces are converted back to electrical signals. Arrays of transducers enable beam steering and imaging.

Applications: Medical imaging uses ultrasound to visualize soft tissues and fetal development; Doppler techniques measure blood flow. Therapeutically, high-intensity focused ultrasound can ablate tissue. Industrial uses include nondestructive testing of welds and materials, cleaning, and processing in sonochemistry. Ultrasonen are also used in sonar and depth sounding.

Principles and safety: Imaging relies on time-of-flight and echo amplitudes; therapy uses focused energy to heat or disrupt tissue. Cavitation and acoustic streaming are non-linear effects at high power and must be managed. Safety guidelines limit exposure to avoid thermal and mechanical hazards; devices adhere to standards from IEC and other regulatory bodies.

History: Early 20th-century work on sonar led to practical ultrasound generation and detection. Medical ultrasonography expanded in the mid-20th century and has since become a routine diagnostic tool with diverse imaging modalities.