Nominal level is the operating level at which an electronic

signal processing Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing '' signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...

device is designed to operate. The

electronic circuit An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electric ...

s that make up such equipment are limited in the maximum signal they can handle and the low-level internally generated electronic noise they add to the signal. The difference between the internal noise and the maximum level is the device's

dynamic range Dynamic range (abbreviated DR, DNR, or DYR) is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of signals, like sound and light. It is measured either as a ratio or as a base ...

. The nominal level is the level that these devices were designed to operate at, for best dynamic range and adequate headroom. When a signal is chained with improper

gain staging In audio engineering, a gain stage is a point during an audio signal flow that the engineer can make adjustments to the level,Thompson, Dan (2005). ''Understanding Audio''. Berklee Press. . such as a fader on a mixing console or in a DAW. Gain st ...

through many devices, clipping may occur or the system may operate with reduced dynamic range. In audio, a related measurement,

signal-to-noise ratio Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in de ...

, is usually defined as the difference between the nominal level and the noise floor, leaving the headroom as the difference between nominal and maximum output. It is important to realize that the measured level is a time average, meaning that the peaks of audio signals regularly exceed the measured average level. The headroom measurement defines how far the peak levels can stray from the nominal measured level before clipping. The difference between the peaks and the average for a given signal is the crest factor.

Standards

VU meter A volume unit (VU) meter or standard volume indicator (SVI) is a device displaying a representation of the signal level in audio equipment. The original design was proposed in the 1940 IRE paper, ''A New Standard Volume Indicator and Reference Lev ...

s are designed to represent the perceived

loudness In acoustics, loudness is the subjective perception of sound pressure. More formally, it is defined as, "That attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of ph ...

of a passage of music, or other audio content, measuring in volume units. Devices are designed so that the best signal quality is obtained when the meter rarely goes above nominal. The markings are often in dB instead of "VU", and the reference level should be defined in the device's manual. In most professional recording and

sound reinforcement A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers in enclosures all controlled by a mixing console that makes live or pre-recorded sounds louder and may also distribute those sounds ...

equipment, the nominal level is . In semi-professional and domestic equipment, the nominal level is usually −10 dBV. This difference is due to the cost required to create larger power supplies and output higher levels. In

broadcasting Broadcasting is the distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum (radio waves), in a one-to-many model. Broadcasting began wi ...

equipment, this is termed the Maximum Permitted Level, which is defined by

European Broadcasting Union The European Broadcasting Union (EBU; french: Union européenne de radio-télévision, links=no, UER) is an alliance of public service media organisations whose countries are within the European Broadcasting Area or who are members of the C ...

standards. These devices use

peak programme meter A peak programme meter (PPM) is an instrument used in professional audio that indicates the level of an audio signal. Different kinds of PPM fall into broad categories: *True peak programme meter. This shows the peak level of the waveform no ...

s instead of VU meters, which gives the reading a different meaning. " Mic level" is sometimes defined as −60 dBV, though levels from microphones vary widely.Extron Electronics Glossary of Terms definition of ''nominal level''
/ref> In

video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) sy ...

systems, nominal levels are 1 V_P-P for synched systems, such as baseband

composite video Composite video is an analog video signal format that carries standard-definition video (typically at 525 lines or 625 lines) as a single channel. Video information is encoded on one channel, unlike the higher-quality S-Video (two channe ...

, and 0.7 V_P-P for systems without sync. Video Signal Standards and Conversion Page
- "The Y signal has a nominal level of 1Vpp and C signal a level of around 0.5V.", "The nominal signal level is 1Vpp on a 75 ohm terminated line." Note that these levels are measured peak-to-peak, while audio levels are time averages.

References

External links

Nominal Level
— Sweetwater glossary

Signal processing Sound

Standards

See also

References

External links