Ultraheli

Ultraheli refers to mechanical waves or vibrations with frequencies above the upper limit of human hearing, typically above about 20 kHz. In practical use, ultrasound covers a wide range of frequencies, with diagnostic imaging often using 2–18 MHz and industrial or therapeutic applications using higher or lower ranges depending on depth and effect.

Generation and detection of ultraheli rely on piezoelectric transducers, which convert electrical energy into high-frequency mechanical waves and, on return, convert echoes back into electrical signals. As waves propagate through media, they are reflected, refracted, attenuated, or scattered at boundaries between different tissues or materials. By analyzing the echoes, ultrasound devices create real-time images or measure properties such as flow or tissue stiffness in some modes.

Medical applications are the most common use of ultraheli. Diagnostic ultrasound uses reflected echoes to visualize organs and developing fetuses, assess organs such as the heart and blood vessels, and guide procedures. Doppler ultrasound measures movement, such as blood flow, and can help diagnose vascular conditions. Therapeutic uses include high-intensity focused ultrasound (HIFU) for targeted tissue ablation and lower-intensity ultrasound for physiological therapy and bone healing.

Industrial and scientific uses include nondestructive testing of metals and composites, thickness measurements, ultrasonic cleaning, welding and machining, and sonochemistry. Safety guidelines emphasize exposure limits and the ALARA principle to minimize risk, since excessive energy can cause heating or cavitation effects.

Historically, ultrasound entered medical practice in the mid-20th century, evolving from early research into imaging and diagnostic applications. Today it remains a versatile tool across medicine, industry, and science.