20kHz

20kHz, or 20,000 Hertz, represents a frequency of 20,000 cycles per second. This value is significant as it marks the upper limit of human hearing for most young, healthy individuals. The range of human hearing is typically considered to be between 20 Hertz and 20,000 Hertz. As people age, or due to prolonged exposure to loud noises, the upper limit of hearing often decreases, meaning older adults may not be able to perceive sounds at or above 20kHz.

Frequencies above 20kHz are classified as ultrasound. These high-frequency sound waves are inaudible to humans but are commonly used in various applications. Medical ultrasound imaging, for example, utilizes ultrasound waves to create images of internal body structures. In industry, ultrasound is employed for non-destructive testing to detect flaws in materials, and in cleaning applications, where the vibrations can dislodge contaminants. Animals such as bats and dolphins use ultrasound for echolocation, navigating and hunting in their environments. The study of sound and its properties, including frequencies like 20kHz, falls under the discipline of acoustics. While 20kHz itself is a specific frequency, it serves as a boundary that distinguishes audible sound from the ultrasonic spectrum, each with its own set of properties and applications.