It is the number of cycles per second, represented by units as s -1, also called hertz, Hz.
The spectrum contains just one component, at 256 Hz, because the pure tone is a single sine wave.
Some of the larger hotels in the cities also have 100 vac / 60 Hz power outlets to cater for visitors from North America.
This refresh rate has to be a minimum of 70 Hz so your eyes won't tire and can't detect screen flickering.
Humans can hear sounds in the frequency or pitch range of 20 to 20,000 Hertz (Hz), but most conversations occur between 300 and 3000 Hz.
