"Duty cycle" is a term used in engineering and manufacturing to describe the given amount of time during which a machine is active. In some cases, it is simply used to determine the value and productivity of a given device and the people using that device. In others, a machine's duty cycle actually represents the amount of time during which the machine can be safely used without becoming damaged or harming its user. Some equipment, for instance, releases a substantial amount of heat and can only be used for a few straight minutes before it must be allowed to cool down for some period of time. The duty cycle, then, can be used as an indication of a given device's efficiency.
The duty cycle of a given piece of machinery can be determined mathematically by dividing the amount of time that the device is active by some unit of time of interest. Something that can run for five minutes out of each 15 minutes but must cool down for the remaining ten minutes, for instance, has a duty cycle of one-third, or 33.3 percent. This figure can be used to compare the efficiency of different devices or to determine how to best use a particular piece of machinery. In general, one tries to use a given piece of machinery for the maximum amount of time possible in order to get the most value from it.
Electronics, communications, and other fields that involve the use of periodic pulses often use the duty cycle to measure various properties of a device or system. Some devices, for instance, send out periodic signals in pulses, and therefore are neither active nor consuming energy at a constant rate. The duty cycle allows one to measure the active time and the average energy consumption over a period of time.
Even music, particularly modern electronic music, sometimes uses the duty cycle in order to make measurements concerning some of the sounds produced. The frequency of particular sounds, which can be represented as oscillating waves, can be changed by altering the duty cycles, often causing subtle changes in the particular sound of the music. Such subtle alterations are generally not used in more traditional forms of music without significant electronic effects, such as classical music, jazz, blues, and many forms of rock. Modern electronic music or music with strong electronic aspects, such as dance music, modern pop, and some forms of rock do use small changes in duty cycles to influence their sounds.