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Loudness monitoring

Loudness monitoring

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Loudness monitoring of programme levels is needed in radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

 and television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...

, as well as in audio post production
Audio post production
Audio post production is the general term for all stages of production happening between the actual recording in a studio and the completion of a master recording. It involves, sound design, sound editing, audio mixing, and the addition of effects.-Film:...

. Traditional methods of measuring signal levels such as the Peak programme meter
Peak programme meter
A peak programme meter is an instrument used in professional audio for indicating the level of an audio signal.There are many different kinds of PPM. They fall into broad categories:...

, and VU meter
VU meter
A VU meter is often included in audio equipment to display a signal level in Volume Units; the device is sometimes also called volume indicator ....

 do not give the subjectively valid measure of loudness
Loudness is the quality of a sound that is primarily a psychological correlate of physical strength . 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."Loudness, a subjective measure, is often...

 which many would argue is needed to optimise the listening experience when changing channels or swapping disks.

The need for proper loudness monitoring is apparent in the loudness war
Loudness war
The loudness war or loudness race is a pejorative term for the apparent competition to digitally master and release recordings with increasing loudness.The phenomenon was first reported with respect to mastering practices for 7" singles...

 that is now found everywhere in the audio field, and the extreme compression that is now applied to programme levels.

Loudness meters

Meters have been introduced that aim to measure the human perceived loudness by taking account of the equal-loudness contours and other factors, such as audio spectrum, duration, compression and intensity. One such device was developed by CBS Laboratories
CBS Laboratories
CBS Laboratories or CBS Labs was the technology research and development organization of CBS...

in the 1980s. Complaints to broadcasters about the intrusive level of interstitials programs (advertisements, commercials) has resulted in projects to develop such meters, that are rapidly going to become fundamental tools for loudness monitoring in the broadcast industry. Based on loudness metering, many manufacturers have developed real-time audio processors that adjust the audio signal to match a specified target loudness level that preserves volume consistency at home listeners.

EBU Mode meters

In August 2010, the European Broadcasting Union published a new metering specification EBU Tech 3341, which builds on ITU-R BS.1770. To make sure meters from different manufacturers provide the same reading, EBU Tech 3341 specifies the 'EBU Mode', which includes a Momentary (400 ms), Short term (3s) and Integrated (from start to stop) meter and a set of audiosignals to test the meters.

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