Final answer:
High-frequency sound waves used for noninvasive medical imaging are called ultrasound, which is utilized in ultrasonography to produce real-time images for patient diagnoses.
Step-by-step explanation:
The high-frequency sound waves in an imaging process used to diagnose patient illness are known as ultrasound. This type of imaging, called ultrasonography, is crucial in medical fields for noninvasive diagnoses, including monitoring fetal development during pregnancy. With a frequency much higher than the highest audible to humans, ultrasound waves are transmitted into the body, and the echo signal returned is converted into real-time images of the body's anatomy and physiology. While ultrasound can also be used for various other medical diagnoses such as heart function and blood flow, it is known for being the least invasive and most freely used imaging technique during sensitive situations like pregnancy.