What types of sound are primarily detected when employing ultrasound testing?

Ultrasound testing is a technique that utilizes sound waves at frequencies higher than the upper limit of human hearing, which is generally above 20 kHz. This high frequency is essential for penetrating materials and detecting flaws or anomalies such as cracks and voids. The primary advantage of high-frequency sounds in ultrasound is their ability to produce more accurate and detailed images or readings when assessing the integrity of materials.

Low frequency sounds, medium frequency sounds, and infrasonic sounds fall below the range typically used in ultrasound testing. Low frequencies may be detected in other non-destructive testing methods, but they do not provide the resolution needed for precise examination. Infrasonic sounds are below 20 Hz and are not relevant to ultrasound which focuses on sound in the higher frequency range. Therefore, the correct answer highlights the specificity of ultrasound technology in utilizing high-frequency sounds for detecting and analyzing various material properties.