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In SI units, the result is measured in hertz (Hz) after the German physicist, Heinrich Rudolf Hertz. 1 Hz means that an event repeats once per second. Other units that have been used to measure frequency include: cycles per second, revolutions per minute (rpm). Heart rate is measured in beats per minute.

An alternative method to calculate frequency is to measure the time between two consecutive occurrences of the event (the period) and then compute the frequency as the reciprocal of this time:

where T is the period.

1 Frequency of waves

Measuring the frequency of sound, electromagnetic waves (such as radio or light), electrical signals, or other waves, the frequency in hertz is the number of cycles of the repetitive waveform per second. If the wave is a sound, frequency is what characterizes its pitch

Frequency has an inverse relationship to the concept of wavelength. The frequency f is equal to the speedFor alternate uses, see Speed (disambiguation). Speed (symbol: v is the rate of motion, or equivalently the rate of change of position, expressed as distance d moved per unit of time t''. Speed is a scalar quantity with dimensions Length/ Time; the equiva v of the waveA wave is a disturbance that propagates. Apart from electromagnetic radiation, and probably gravitational radiation, which can travel through vacuum, waves exist in a medium (which on deformation is capable of producing elastic restoring forces) through w dividedThis article is about the arithmetic operation. For other uses, see Division (disambiguation). In mathematics, especially elementary arithmetic, division is an arithmetic operation which is the reverse operation of multiplication and sometimes can be inte by the wavelength λ (lambda) of the wave:

In the special case of electromagnetic waves moving through a vacuumThe article on the vacuum cleaner is located elsewhere. In physics, a vacuum is the absence of matter in a volume of space. A partial vacuum is expressed in units of pressure. The SI unit of pressure is the pascal (abbreviated to Pa in usage). It can also, then v = c, where c is the speed of lightCherenkov effect in a "swimming pool" nuclear reactor. The effect is due to electrons moving faster than the speed at which light moves in water. The speed of light (denoted as c reputedly from the Latin celeritas "speed", and also known as Einstein's con in a vacuum, and this expression becomes:

2 Statistical frequency

In statisticsStatistics is the science and practice of developing human knowledge through the use of empirical data. It is based on statistical theory which is a branch of applied mathematics. Within statistical theory, randomness and uncertainty are modelled by proba, the frequency of an event is simply the number of times the event occurred in the experiment or the study. These frequencies are often graphically represented in histograms.

3 Examples

• The frequency of the standard pitch tone A above middle C is nowadays set at that is 440 cycles per second (or slightly higher) and known as concert pitch, after which an orchestra is tuned.

• A baby can hear tones with oscillations up to approximately 20,000 Hz. Adults do not hear this high frequency any longer.

• In Europe the frequency of the alternating current is 50 Hz (close to the tone G), with 230 V of rated voltage.

• In America the frequency of the alternating current is 60 Hz (close to the tone B flat), with 117 V of rated voltage.

• From the height of the net-hum tone it is to be recognized whether a sound recording was made e.g. in Europe. In Europe it hums a small third lower than in the USA. An analyzer will find rather the double and the three-fold of that electricity mains frequency and hardly the fundamental in the recording.

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Topics: Frequency Event Time Wave Pitch Tone Sound Waves Number Hertz...

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FrequencyFrequency is the measurement of the number of times that a repeated event occurs per unit time. To calculate the frequency, one fixes a time interval, counts the number of occurrences of the event within that interval, and then divides this count by the l Frequency modulationFM redirects here, for alternate uses, see Fm Frequency modulation (FM) is the encoding of information in either analogue or digital form into a carrier wave by variation of its instantaneous frequency in accordance with an input signal. This is typically Frequency probabilityStatistical regularity has motivated the development of the relative frequency concept of probability. Most of the procedures commonly used to make statistical estimates or tests were developed by statisticians who used this concept exclusively. They are Frequency modulation synthesisA 220 Hz carrier tone modulated by a 440 Hz modulating tone with various choices of modulation index,. The time domain signals are illustrated above, and the corresponding spectra are shown below (spectrum amplitudes in dB). An audio demonstration of the Frequency assignmentIn telecommunication, the term frequency assignment has the following meanings: # Authorization, given by an Administration, for a radio station to use a radio frequency or radio frequency channel under specified conditions. The process of authorizing a s Frequency assignment authorityIn telecommunication, frequency assignment authority is the power granted an Administration, or its designated or delegated leader or agency via treaty or law, to specify frequencies, or frequency bands, in the electromagnetic spectrum for use in systems Frequency averaging Frequency-change signaling Frequency compatibility Frequency deviation Frequency-exchange signaling Frequency frogging Frequency sharing Frequency shift Frequency-shift keying