Frequency

Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency, which emphasizes the contrast to spatial frequency and angular frequency. The period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example, if a newborn baby's heart beats at a frequency of 120 times a minute, its period – the interval between beats – is half a second (60 seconds (i.e., a minute) divided by 120 beats). Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio (sound) signals, radio waves, and light.

Definitions

For cyclical processes, such as rotation, oscillations, or waves, frequency is defined as a number of cycles per unit time. In physics and engineering disciplines, such as optics, acoustics, and radio, frequency is usually denoted by a Latin letter f or by the Greek letter or ν (nu) (see e.g. Planck's formula). The period, usually denoted by T, is the duration of one cycle, and is the reciprocal of the frequency f:

Frequency (video game)

Frequency is a music video game developed by Harmonix and published by SCEA. It is the first major release from Harmonix. It was released in November 2001. A sequel titled Amplitude was released in 2003.

Gameplay

In the game, a player portrays a virtual avatar called a "FreQ", and travels down an octagonal tunnel, with each wall containing a musical track. These tracks contain sequences of notes. As the player hits buttons corresponding to the note placement on the track, the "sonic energy" from within is released and the music plays. If the player plays two measures of the track without any errors, the track is "captured" and the music plays automatically until the next pre-determined section of the song. All songs featured in the game are edited for ease of play.

Some tracks are bonus tracks and only open up when all notes are played, allowing the user to pick up "freestyle" points. Powerups are available which allow the immediate capturing of the track or the doubling of points. If a player continually misses notes, their energy meter reduces until the game is over.

Sound

In physics, sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a medium such as air or water. In physiology and psychology, sound is the reception of such waves and their perception by the brain.

Acoustics

Acoustics is the interdisciplinary science that deals with the study of mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound, and infrasound. A scientist who works in the field of acoustics is an acoustician, while someone working in the field of acoustical engineering may be called an acoustical engineer. An audio engineer, on the other hand is concerned with the recording, manipulation, mixing, and reproduction of sound.

Applications of acoustics are found in almost all aspects of modern society, subdisciplines include aeroacoustics, audio signal processing, architectural acoustics, bioacoustics, electro-acoustics, environmental noise, musical acoustics, noise control, psychoacoustics, speech, ultrasound, underwater acoustics, and vibration.

Visa

Visa or VISA may refer to:

Government

Financial services

Geography

Motor vehicle

Film and TV

Music

Other uses

See also

Évisa

Évisa is a commune in the Corse-du-Sud department of France on the island of Corsica.

Population

See also

References

Visa Inc.

Visa Inc. (/ˈviːzə/ or /ˈviːsə/) is an American multinational financial services corporation headquartered in Foster City, California, United States. It facilitates electronic funds transfers throughout the world, most commonly through Visa-branded credit cards and debit cards. Visa does not issue cards, extend credit or set rates and fees for consumers; rather, Visa provides financial institutions with Visa-branded payment products that they then use to offer credit, debit, prepaid and cash-access programs to their customers. In 2008, according to The Nilson Report, Visa held a 38.3% market share of the credit card marketplace and 60.7% of the debit card marketplace in the United States. In 2009, Visa’s global network (known as VisaNet) processed 62 billion transactions with a total volume of $4.4 trillion.

Visa has operations across India, Australia, Oceania, Asia-Pacific, North America, Central and South America, the Caribbean, Western Europe, Central and Eastern Europe, Africa and Middle East. Visa Europe is a separate membership entity that is an exclusive licensee of Visa Inc.'s trademarks and technology in the European region, issuing cards such as Visa Debit and Visa Credit.