Dolby Laboratories 737 A.3.1 Alternative Measurement Indices

Model 737 Soundtrack Loudness Meter - Leq(m) Background

A-5

A.3.1 Alternative Measurement Indices

As might be expected, the samples yielded different loudness values when assessed

with different systems. The low-frequency roll-off of A-weighting results in a reduction

in Leq when the material has a substantial bass content. Determination of annoyance,

however, does not necessarily match the A-weighting curve. Research at Dolby has

revealed that placing heavier emphasis on the 2–6 kHz region better matches how people

react to soundtrack loudness. It was also discovered that the CCIR-weighting curve

used to measure low-level recording medium noise more closely matched the subjective

annoyance criteria (Figure A-2).

Figure A-2 A-weighting vs. CCIR-weighting curve (offset by 5.6 dB)

Although there is no technical parallel between high-level soundtrack loudness and

low-level recording medium noise, the CCIR curve provided a convenient weighting

filter for the tests and a better subjective match than Leq(a). The CCIR curve can be

further adapted to represent soundtrack loudness by offsetting the level by 5.6 dB, with

a 2 kHz reference point. Loudness values derived from this characteristic are referred

to in this document as Leq(m). Figure A-3 shows the relationship between Leq(m) and

Leq(a) for UK commercials. Although the average values for Leq(m) and Leq(a) are

the same, higher relative Leq(m) values show a signal content with greater emphasis in

the 2–6 kHz region.

CCIR-weighting

A-weighting

dB

+20

+10

0

-10

-20

-30

-40

10

Hz

100 1k 10k 100k

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Contents

Main Dolby Laboratories Inc Table of Contents List of Figures List of Tables Chapter 1 Introduction Chapter 2 Operation and Features Chapter 3 Cat. No. 448B Input Adapter Board Chapter 4 Specifications Appendix A Background List of Figures List of Tables Chapter 1 Introduction Chapter 2 Operation and Features 2.1 Front Panel Controls 6/4 - 2 channel switch Start Trip Set Cal 2.1.1 6/4 2 Channel Switch 2.1.2 Input Trimpots 2.1.3 Trip Set 2.1.4 Pushbuttons Model 737 Soundtrack Loudness Meter - Leq(m) Operation and Features 2.2 Back Panel Connectors Figure 2-3 Model 737 back panel 2.2.1 Analog Audio Inputs Figure 2-4 Audio input connectors (detail of rear panel) The XLR input connectors for channels 16 use the following wiring convention: 2.2.2 Mon Out 2.2.3 DC Out 2.2.4 Power and Control 2.3 Connection and Calibration 2.3.1 Connecting to an Audio Console 2.3.2 Connecting to a Dolby Cinema Processor 2.3.3 Connecting to a DA10/20 Digital Adapter 2.3.4 Connecting to Non-Dolby Digital Adapters 2.3.5 Connecting to the SDU4 Surround Decoder 2.3.6 Calibration Procedure 2.3.7 Automated Input Adapter Board (Cat. No. 448B) 2.4 Mains Power 2.5 Interface 2.5.1 Grounding Model 737 Soundtrack Loudness Meter - Leq(m) Operation and Features 2-10 2.6 Block diagram Figure 2-6 Model 737 block diagram L/Lt C Ls R/Rt Sub Rs Page Chapter 3 Cat. No. 448B Input Adapter Board 3.1 Introduction 3.2 Logic map Model 737 Soundtrack Loudness Meter - Leq(m) Cat. No. 448B Input Adapter Board 3-2 3.3 Component and Connector Layout x2 (Lt/Rt - opt) CAT. NO. 448B Cat. No. 448B Figure 3-1 Cat. No. 448B Interface Adapter 3.4.3 Alignment 3.5 Dubbing studio Page 3.5.1 Alignment Page Chapter 4 Specifications Temperature and Humidity EMC Limits General Appendix A Background A.1 Loudness A.1.1 The Current Situation Page A.2 How Loud Is a Movie? A.3 Standardizing a Measurement Technique for Soundtrack Loudness A.3.1 Alternative Measurement Indices A.4 Analysis of the Data Page Model 737 Soundtrack Loudness Meter - Leq(m) Background A-8 Figure A-5 Comparison of Leq(m) and peak levels Shine demo 1 (Rach. III) Leq CCIR-weighted Peak Level C-weighted, fast 5.6 dB offset dB A.4.1 Verification of the Data Leq CCIR-weighted Peak Level C-weighted, fast