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Frequency

Frequency (symbol f), most often measured in hertz (symbol: Hz), is the number of occurrences of a repeating event per unit of time.[1] It is also occasionally referred to as temporal frequency for clarity and to distinguish it from spatial frequency. Ordinary frequency is related to angular frequency (symbol ω, with SI unit radian per second) by a factor of 2π. The period (symbol T) is the interval of time between events, so the period is the reciprocal of the frequency: f = 1/T.[2]

"Frequencies" redirects here. For the film, see Frequencies (film). For the album, see Frequencies (album). For other uses, see Frequency (disambiguation).

Frequency

f, ν

hertz (Hz)

s−1

  • f = 1 / T

Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light.


For example, if a heart beats at a frequency of 120 times per minute (2 hertz), the period—the interval between beats—is half a second (60 seconds divided by 120 beats).

usually denoted by the Greek letter ν (nu), is defined as the instantaneous rate of change of the number of rotations, N, with respect to time: ν = dN/dt; it is a type of frequency applied to rotational motion.

Rotational frequency

usually denoted by the Greek letter ω (omega), is defined as the rate of change of angular displacement (during rotation), θ (theta), or the rate of change of the phase of a sinusoidal waveform (notably in oscillations and waves), or as the rate of change of the argument to the sine function:

Angular frequency

Aperiodic frequency[edit]

Aperiodic frequency is the rate of incidence or occurrence of non-cyclic phenomena, including random processes such as radioactive decay. It is expressed with the unit of reciprocal second (s−1)[13] or, in the case of radioactivity, becquerels.[14]


It is defined as a rate, f = N/Δt, involving the number of entities counted or the number of events happened (N) during a given time duration (Δt); it is a physical quantity of type temporal rate.

Davies, A. (1997). . New York: Springer. ISBN 978-0-412-61320-3.

Handbook of Condition Monitoring: Techniques and Methodology

Serway, Raymond A.; Faughn, Jerry S. (1989). . London: Thomson/Brooks-Cole. ISBN 978-05344-0-814-5.

College Physics

Young, Ian R. (1999). . Elsevere Ocean Engineering. Vol. 2. Oxford: Elsevier. ISBN 978-0-08-043317-2.

Wind Generated Ocean Waves

Giancoli, D.C. (1988). Physics for Scientists and Engineers (2nd ed.). Prentice Hall.  978-0-13-669201-0.

ISBN

Keyboard frequencies = naming of notes – The English and American system versus the German system

A frequency generator with sound, useful for hearing tests