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Hertz, Hertz

It is defined as the number of cycles per second. It is the basic unit of frequency in the International System of Units (SI), and is used worldwide in both general-purpose and scientific contexts. Hertz can be used to measure any periodic event; the most common uses for hertz are to describe radio and audio frequencies, more or less sinusoidal contexts in which case a frequency of 1 Hz is equal to one cycle per second.

Hertz are inverse, s -1 . In practice, the hertz simply replaced the older cycle per second.

As any SI unit, Hz can be prefixed; commonly used multiples are kHz (kilohertz, 10 3 Hz), MHz (megahertz, 10 6 Hz), GHz (gigahertz, 10 9 Hz) and THz (terahertz, 10 12 Hz). One hertz simply means "one cycle per second" (typically that which is being counted is a complete cycle); 100 Hz means "one hundred cycles per second", and so on. The unit may be applied to any periodic eventfor example, a clock might be said to tick at 1 Hz, or a human heart might be said to beat at 1.2 Hz. Neither the cycle per second nor the hertz, however, are regularly used in nonsinusoidal contexts. The "frequency" (activity) of aperiodic or stochastic events, especially radioactive decay, is expressed in becquerels.

The term cycles per second was largely replaced by hertz by the 1970s.

Humans perceive frequency of sound waves as pitch. Each musical note corresponds to a particular frequency which can be measured in hertz. An infant's ear is able to perceive frequencies ranging from 16 Hz to 20,000 Hz; the average human can hear sounds between 20 Hz and 16,000 Hz.

This number refers to the frequency of the CPU's master clock signal ("clock speed"). This signal is simply an electrical voltage which changes from low to high and back again at regular intervals. Hertz has become the primary unit of measurement accepted by the general populace to determine the speed of a CPU, but many experts have criticized this approach, which they claim is an easily manipulable benchmark.

For practical reasons, these are typically not expressed in hertz, but in terms of the equivalent quantum energy, which is proportional to the frequency by the factor of Planck's constant.

Source: Wikipedia > Hertz