In electronics

Electronics

Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

, signal processing

Signal processing

Signal processing is an area of systems engineering, electrical engineering and applied mathematics that deals with operations on or analysis of signals, in either discrete or continuous time...

, and video, ringing is unwanted oscillation

Oscillation

Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...

 of a signal, particularly in the step response

Step response

The step response of a system in a given initial state consists of the time evolution of its outputs when its control inputs are Heaviside step functions. In electronic engineering and control theory, step response is the time behaviour of the outputs of a general system when its inputs change from...

 (the response to a sudden change in input). It is also known as hunting. It is closely related to overshoot

Overshoot (signal)

In signal processing, control theory, electronics, and mathematics, overshoot is when a signal or function exceeds its target. It arises especially in the step response of bandlimited systems such as low-pass filters...

, generally occurring following overshoot, and thus the terms are at time conflated.

It is also known as ripple, particularly in electricity or in frequency domain

Frequency domain

In electronics, control systems engineering, and statistics, frequency domain is a term used to describe the domain for analysis of mathematical functions or signals with respect to frequency, rather than time....

 response.

Electricity

In electrical

Electricity

Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 circuits, ringing is an unwanted oscillation

Oscillation

Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...

 of a voltage

Voltage

Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...

 or current. It happens when an electrical pulse causes the parasitic capacitances

Capacitor

A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...

 and inductances

Inductor

An inductor is a passive two-terminal electrical component used to store energy in a magnetic field. An inductor's ability to store magnetic energy is measured by its inductance, in units of henries...

 in the circuit (i.e. those that are not part of the design, but just by-products of the materials used to construct the circuit) to resonate

Resonance

In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...

 at their characteristic frequency

Frequency

Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...

. Ringing artifacts are also present in square wave

Square wave

A square wave is a kind of non-sinusoidal waveform, most typically encountered in electronics and signal processing. An ideal square wave alternates regularly and instantaneously between two levels...

s; see Gibbs phenomenon

Gibbs phenomenon

In mathematics, the Gibbs phenomenon, named after the American physicist J. Willard Gibbs, is the peculiar manner in which the Fourier series of a piecewise continuously differentiable periodic function behaves at a jump discontinuity: the nth partial sum of the Fourier series has large...

.

Ringing is undesirable because it causes extra current to flow, thereby wasting energy and causing extra heating of the components; it can cause unwanted electromagnetic radiation

Electromagnetic radiation

Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

 to be emitted; it can delay arrival at a desired final state (increase settling time

Settling time

The settling time of an amplifier or other output device is the time elapsed from the application of an ideal instantaneous step input to the time at which the amplifier output has entered and remained within a specified error band, usually symmetrical about the final value.Settling time includes a...

); and it may cause unwanted triggering of bistable elements in digital circuit

Digital circuit

Digital electronics represent signals by discrete bands of analog levels, rather than by a continuous range. All levels within a band represent the same signal state...

s. Ringy communications circuits may suffer falsing

Falsing

In telecommunications, falsing describes a decoder assuming that it is detecting a valid input when one is not present. This is also known as a false decode...

.

Ringing can be due to signal reflection

Signal reflection

Signal reflection occurs when a signal is transmitted along a transmission medium, such as a copper cable or an optical fiber, some of the signal power may be reflected back to its origin rather than being carried all the way along the cable to the far end. This happens because imperfections in the...

, in which case it may be minimized by impedance matching

Impedance matching

In electronics, impedance matching is the practice of designing the input impedance of an electrical load to maximize the power transfer and/or minimize reflections from the load....

.

Video

In video circuits, electrical ringing causes closely spaced repeated ghosts

Ghosting (television)

In television, a ghost is a replica of the transmitted image, offset in position, that is super-imposed on top of the main image on an analogue broadcast.-Common causes:Common causes of ghosts are:...

 of a vertical or diagonal edge where dark changes to light or vice versa, going from left to right. In a CRT

Cathode ray tube

The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

 the electron beam upon changing from dark to light or vice versa instead of changing quickly to the desired intensity and staying there, overshoots and undershoots a few times. This bouncing could occur anywhere in the electronics or cabling and is often caused by or accentuated by a too high setting of the sharpness control.

Audio

Ringing affects audio equipment in two ways. Audio electronics have the same ringing issues as do all electronic equipment, with the exception that the ringing may be audible. In addition, transducers (ie, microphones and loudspeakers) can also ring. Arguably, mechanical ringing is more of a problem with loudspeakers as the moving masses are larger and less easily damped. Mechanical ringing, unless extreme is difficult to audibly identify as such. It is usually noted as a like of characteristic 'coloration' in the sound and is very hard to describe in words.

An additional effect often heard in sound reproduction is sometimes referred to as ringing, but is in fact a kind of feedback

Audio feedback

Audio feedback is a special kind of positive feedback which occurs when a sound loop exists between an audio input and an audio output...

. This is a piercing squeal or screech, caused by loudspeaker output being picked up by one or more microphones and passed through the amplifier and back to the loudspeakers again. Given a particular sound system and a particular room, some frequency will be emphasized, will be the first to 'runaway' in a positive feedback

Feedback

Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...

 condition, and will cause the screech. A system on the verge of runaway feedback often has a peculiar wavery, ringy quality as it goes almost into and then somewhat away from actual runaway feedback.

Signal processing

In signal processing

Signal processing

Signal processing is an area of systems engineering, electrical engineering and applied mathematics that deals with operations on or analysis of signals, in either discrete or continuous time...

, "ringing" may refer to ringing artifacts

Ringing artifacts

In signal processing, particularly digital image processing, ringing artifacts are artifacts that appear as spurious signals near sharp transitions in a signal. Visually, they appear as bands or "ghosts" near edges; audibly, they appear as "echos" near transients, particularly sounds from...

: spurious signals near sharp transitions. These have a number of causes, and occur for instance in JPEG

JPEG

In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....

 compression and as pre-echo

Pre-echo

Pre-echo is a digital audio compression artifact where a sound is heard before it occurs . It is most noticeable in impulsive sounds from percussion instruments such as castanets or cymbals....

in some audio compression.

External links

• Microphony with older video cameras