In acoustics, a beat is an interference between two sounds of slightly different frequencies, perceived as periodic variations in volume whose rate is the difference between the two frequencies.

With tuning instruments that can produce sustained tones, beats can readily be recognized. Tuning two tones to a unison will present a peculiar effect: when the two tones are close in pitch but not yet identical, the difference in frequency generates the beating. The volume varies like in a tremolo as the sounds alternately interfere constructively and destructively. When the two tones gradually approach unison, the beating slows down and disappears.

This phenomenon manifests acoustically. If a graph is drawn to show the function corresponding to the total sound of two strings, it can be seen that maxima and minima are no longer constant as when a pure note is played, but change over time: when the two waves are nearly 180 degrees out of phase the maxima of each cancel the minima of the other, whereas when they are nearly in phase their maxima sum up, raising the perceived volume.

Beat may refer to:

Acoustics is the interdisciplinary science that deals with the study of all 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 acoustics technology may be called an acoustical engineer. The application of acoustics can be seen in almost all aspects of modern society with the most obvious being the audio and noise control industries.

Hearing is one of the most crucial means of survival in the animal world, and speech is one of the most distinctive characteristics of human development and culture. So it is no surprise that the science of acoustics spreads across so many facets of our society—music, medicine, architecture, industrial production, warfare and more. Art, craft, science and technology have provoked one another to advance the whole, as in many other fields of knowledge. Robert Bruce Lindsay's 'Wheel of Acoustics' is a well accepted overview of the various fields in acoustics.

Justin Drew Bieber ( /ˈbiːbər/ BEE-bər, born March 1, 1994) is a Canadian Pop/R&B singer-songwriter, musician, and actor. Bieber was discovered in 2008 by Scooter Braun, who came across Bieber's videos on YouTube and later became his manager. Braun arranged for him to meet with Usher in Atlanta, Georgia, and Bieber was soon signed to Raymond Braun Media Group (RBMG), a joint venture between Braun and Usher, and then to a recording contract with Island Records offered by L.A. Reid. Bieber's debut single, "One Time", was released in 2009 and peaked in the top twenty in Canada and charted in the top thirty in several international markets. His debut album, the seven-track EP My World, followed in November 2009, and was soon certified platinum in the United States. He became the first artist to have seven songs from a debut album chart on the Billboard Hot 100.

Oliver "Olly" Stanley Murs (born 14 May 1984 in Witham, Essex, England) is an English singer-songwriter, musician and TV presenter. Murs rose to fame after being the runner-up on the sixth series of The X Factor. He is currently signed to Epic Records and Syco Music.

In late August 2010, Murs released his debut single "Please Don't Let Me Go", which debuted at number one on the UK Singles Charts, becoming Murs' second number one single after releasing "You Are Not Alone" with the other series 6 finalists. "Please Don't Let Me Go" received a Silver certification by the BPI. He released his second single from his debut album "Thinking of Me" which charted at number four on the UK Singles Charts, however the single also got a Silver certification by the BPI. "Heart Skips a Beat" was released and became his third number-one hit. Murs' second single from his follow up album In Case You Didn't Know, "Dance with Me Tonight", became his fourth to reach number one.

In November 2010, Murs released his self-titled debut album, which entered the UK Albums Chart at number two, with the biggest week one album sales for a debut album in 2010, with over 108,000 albums sold. The album went on to sell over 600,000 copies, and was certificated double platinum by the BPI. In November 2011, Murs released his second album, In Case You Didn't Know. The album entered the charts at number one, and has spawned two number one singles. In May 2011, it was announced that Murs would return to The X Factor to co-present spin-off show The Xtra Factor with Caroline Flack. It was also confirmed that Murs would present a Celebrity Club Classic show on Heart FM. He also has an active Twitter account with over 2 million followers as of May 2012.