Control of Loudness - LEQ Programme

1
Control of Loudness -LEQ Programme

• Julian Pinn,
• Senior Sound Consultant,
• Dolby Laboratories Inc.

2
Overview

• Typical Natural Sound Levels
• Fundamental Issue
• Solution Dolby Model 737
• Current news
• Discussion

3
Typical Natural Sound Levels
4
Fundamental Issue

• Peak recording levels (headroom) was being used
  for average record levels of many competitive
  spots.
• Loss of standard replay level.
• Loss of dynamic range, thus quality.
• Independent peak-limitation did nothing for
  quality, and caused difficulty for international
  releases.

5
Solution

• Research the most suitable way of measuring the
  perceived loudness and annoyance of a section of
  film sound.
• Produce a tool to be able to measure this new
  limitation.
• Establish a world-wide standard.

6
Dolby Model 737Soundtrack Loudness Meter - Leq(m)

• Time averaging
• Frequency weighted curve
• Cheap and easy to install
• 5.1 compatible

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Dolby Model 737Soundtrack Loudness Meter - Leq(m)
dBSPL

• Time averaging

110
105
100
95
90
85
80
75
Time
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Dolby Model 737Soundtrack Loudness Meter - Leq(m)

• Frequency weighting

9
Current news

• Trailer Audio Standards Association requires a
  limit of all US trailers to 85 dBLeq(m).
• Screen Advertising World Association recommends a
  limitation of all commercials to 82 dBLeq(m).
• The British Standard (BS5550 7.4.2) specifies the
  Leq(m) system and the currently practiced
  industry levels.
• An International Standards Organization (ISO) new
  work item specifies Leq(m) for perceived loudness
  assessment.
• Motion Picture Loudness Committee obtained
  agreement between Dolby, dts, and SDDS that all
  UK trailers and commercials be rejected that
  exceed BS5550 7.4.2.
• Many screen advertisers standardized on 82
  dBLeq(m) and Dolby Digital as the commercial
  release format.
• Dolby Laboratories Inc. (RoW) require all cinema
  commercials and film trailers to be mastered in
  accordance with BS5550 7.4.2 from 1 January 2002.

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Control of Loudness -LEQ Programme

• Julian Pinn,
• Senior Sound Consultant,
• Dolby Laboratories Inc.