hertz

That many vibrations in 1 second?

Symbol: Hz / Base data: Frequency, vibration frequency. SI derived unit.
Unit used for periodic phenomena in which the same vibration waveform is repeated for a certain time. If it repeats n-times in a second, it will be n-hertz

Humans can hear 20 to 20,000 hertz

Frequency expresses the frequency of vibrations repeated over a certain cycle, such as sound and radio waves. The number of times such waves vibrate in one second is expressed as a number. If it is 1 vibration per second, it will be expressed as 1Hz. The frequency of sounds in the audible range of humans is 20 to 20,000 Hz. The platinum frequency band of a cellphone is a radio wave of 800 MHz.