Compared to audible sound waves, ultrasound waves have

Sound waves are categorized based on their frequency ranges. Audible sound waves for humans typically fall between 20 Hz and 20,000 Hz (20 kHz). Ultrasound is defined as sound waves with a frequency above the upper limit of human hearing, specifically greater than 20 kHz. While ultrasound has a higher frequency, its speed is not inherently higher than audible sound; the propagation speed of any acoustic wave is determined by the properties of the medium, such as density and stiffness, rather than the frequency itself. Furthermore, because wavelength is inversely proportional to frequency (v = fλ), ultrasound waves actually have shorter wavelengths compared to audible sound waves in the same medium. Therefore, the distinguishing characteristic of ultrasound compared to audible sound is its higher frequency.