Dolby Laboratories 737 Appendix A Background, A.1 Loudness

Model 737 Soundtrack Loudness Meter - Leq(m)

A-1

Appendix ABackground

This Appendix is an edited version of a paper published in the January 1998 SMPTE Journal (Volume 107, Number

1) entitled “Are Movies Too Loud” by Ioan Allen. The complete paper is available from the Dolby website at

www.dolby.com/movies. Reprints of the paper are available by sending email to info@dolby.com (include the article

title) or by calling 415-558-0200.

Over the past few years, the film production community has become increasingly

concerned that movies are getting louder. In addition, movie-goers often complain that

movies are too loud and, as a result, many theatres now reduce the audio fader below the

calibration level used in the dubbing theatre.

This chapter introduces some of the issues that motivated the creation of the Dolby

Model 737 Soundtrack Loudness Meter - Leq(m):

•What factors affect soundtrack “loudness?”

•How can loudness be quantified?

•Do new sound formats (Dolby SR, Dolby SR·D, Sony SDDS, and DTS) exacerbate

the problem?

A.1 Loudness

Those familiar with movie soundtracks won’t be surprised at the subjective statement

that The Right Stuff (1983; Dolby A-type 70 mm and Dolby A-type stereo optical) was

a loud movie. The Right Stuff was a subjectively louder movie than Shine (1996, Dolby

Digital). Since Shine was subjectively louder than Days of Heaven (1978), perhaps a

case could be made that movies have been getting both louder and quieter! Of course,

this does not lead to an objective assessment; selected titles can be used to prove either

trend. Gone with the Wind (1939) could be used to argue that films have become quieter

over the last six decades!

In the mid-1970s, Dolby Laboratories introduced a calibration recommendation for

monitor levels in movie soundtracks. A pink noise reference signal was used in the

record chain to adjust the audio monitor level to 85 dBc. All theatres equipped for play-

back of the new stereo optical soundtracks were set up such that an equivalent pink

noise signal would generate the same 85 dBc with the playback fader set to the calibrat-

ed setting. This meant that theatres playing films at the calibrated fader setting (fader 7

on most cinema processors) would reproduce the same volume level selected by the

film director and audio engineers in the dubbing theatre.

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