Translation with SYSTRAN Links
Sound intensity of television

Glossary

Program : a set of animated images, combined with sound, component only one element within the framework of a grid. A program can be for example a film, a sporting event, a sitcom, documentary, a program for children or an original fiction. 

Auto--promotion : sequence briefly presenting images drawn from the programs headlights of a chain, to some extent constituting the window of the latter.

Trailer : sequence having the aim of announcing the nearest diffusion, on the antenna of a chain, a given program.

Advertisement : according to article 2 of the decree n° 92-280 of the modified March 27th, 1992 “(…) constitute a publicity any form of televised message diffused subject to remuneration or another counterpart in sight is to promote the supply of goods or services, including those which are presented, under their a generic, within the framework of marketing activity, industrial, artisanal name or of liberal profession, that is to say to ensure the sales promotion of a public enterprise or private”. 

Sound volume : this term refers sometimes to the maximum amplitude or peak of an audio sequence (cf operates by remote control of a television set), sometimes with the appreciably different concept which is the energy transmitted by the loudspeakers in acoustic pressure towards the ears of the televiewer.

The perceived sound intensity is function of the energy transmitted by a sound, and translated by the loudspeakers into acoustic pressure. This size conditions the sound perception of the televiewer, which can vary from one individual to another, and from one moment to another.

The sound intensity short time corresponds to the value of the sound intensity of an audio sequence measured on a slipping window three seconds.

The average sound intensity of an audio sequence is the average of the measured values of sound intensity short time of the beginning at the end of the sequence.

The peak values are the extreme values between which all the instantaneous values of a sound track are registered. The remote control of a receiver makes it possible to apply a multiplying factor to these values, which makes it possible to modify the perceived sound intensity, while preserving the sound dynamics of the sequence. With peak values constants, it is on the other hand possible to obtain different perceived intensities, by reducing sound dynamics.

The sound dynamics of an audio sequence is the difference between the values minimal and maximum which the sound intensity short time during a sequence can take. This value is not modified at the time of an action by the televiewer on the keys “volume” of a remote control, since this operation preserves unchanged the reports of sound intensities short time of the sequence but modifies the values minimal and maximum. The more dynamics is raised, the more ventilated the sound appears, and the less it is perceived like “fort”, with peak values constants by the televiewers. A contrario, more dynamics is weak, more the sound appears like “fort” to the televiewer.

Dynamic compression or reduction of the sound dynamics of an audio sequence is a process modifying the values of intensity short time while preserving the maximum value in order to increase the average sound intensity. The sequence is then perceived as “stronger” by the televiewer whereas the “volume” fixed thanks to the remote control remains unchanged.

An isosonic curve of weighting makes it possible to calculate the contribution of each frequency constitutive of a sound the sound impression of energy which it releases at the time of its listening under conditions given. The curve of weighting which is retained to characterize this impression within the framework of measurement the sound intensity in television is the curve K.

 

Parameter LRA characterizes the statistical distribution of the sound intensities short time measured in an audio sequence.

LUFS indicates the measuring unit full scale of sound intensity of an audio sequence according to an isosonic curve of weighting K. scale LUFS is graduated by step of 1 LU, equivalent to a step of 1 dB.

LU indicates the unit of variation of the sound intensity of an audio sequence.