LM 100The Dolby® LM100 Broadcast Loudness Meter is a tool for measuring the subjective loudness of dialogue within broadcast programming.
Differences in audio levels between programs, or between programs and commercials, are a major annoyance to TV viewers. However, although obvious to the viewer, these differences have proven difficult for broadcasters to measure with conventional methods and equipment. The Dolby LM100 Broadcast Loudness Meter solves that problem through Dialogue IntelligenceT, a revolutionary technology developed specifically to measure the perceived loudness of dialogue. Research shows that most viewers adjust TV volume to normalize dialogue levels. By analyzing the input signal and measuring program loudness only during the presence of speech, Dialogue Intelligence objectively measures what viewers subjectively experience.
Dolby LM100 Applications
Applications for the LM100 range from postproduction and quality control to final transmission, program turnaround, and cable head-end facilities.
Easy-to-Read Measurements on the LM100
The LM100 can use ITU-R BS.1770-1 and BS.1770-2 as the core measurement algorithm. Users can also select Leq(A) or EBU R128. For units manufactured prior to September 2011, Dolby offers a software upgrade option that adds the latest features, including the ITU-R BS.1770-2 algorithm.
The LM100 presents its measurements in an easy-to-understand numerical format. This eliminates the variations in results that multiple operators often find when using VU or PPM meters, neither of which was designed to measure subjective loudness. The LM100 can also determine the unweighted peak and a range of other information about the signal, including the Loudness Range measurement specified by the EBU. The unit can simultaneously display the incoming dialogue normalization (dialnorm) value of a Dolby Digital program (or any program within a Dolby E bitstream) for direct comparison to the actual measured value.
Front- and rear-panel serial interfaces provide capabilities for software updates and the LM100 software remote application. The remote application will assist users with advanced loudness measurement, logging features, and enhanced error reporting.
A set of user-definable alarms and monitoring functions can inform an operator of input loss, signal clipping, overmodulation (LM100-NTSC version), high or low signal levels, silence, and incorrectly set dialnorm values.
Dolby LM100 Configurations
The LM100-LTC includes a timecode input, which allows alarm and other signal conditions to be logged to either the internal time-of-day clock or external timecode. The LM100-NTSC includes an RF input specifically for NTSC CATV and “off-air” television measurement applications. Because the RF tuner replaces the linear timecode input in this version, logging is referenced to the internal clock.
Core Measurement Algorithm (User Selectable)
Dialogue Intelligence Algorithm
Proprietary; patent pending
Audio Sampling Rates
32, 44.1, and 48 kHz
Measurement/Analysis System Log
480 events stored in internal nonvolatile RAM
Unlimited event storage and retrieval with use of LM100 software remote application on a PC
90-264 VAC, 50-60 Hz, auto-sensing, 15 W maximum; designed to operate from a centrally switched power source
Dimensions and Weight
1-U rackmount: 44 × 483 × 375 mm (1.75 × 19 × 14.75 inches)
Net: 2.5 kg (5.5 lb)
Operating: 0°C-50°C (32°F-122°F), natural convection cooling, 0%-98% relative humidity (noncondensing)
Nonoperating: -20°C to +70°C (-4°F to 158°F)
North America: This unit complies with the limits for a Class A digital device pursuant to Part 15 of the FCC rules and Industry Canada ICES-003 Class A requirements. It is UL Listed for the US and Canada.
Europe: This unit complies with the requirements of Low Voltage Directive 73/23/EEC and EMC Directive 89/336/EEC and carries the CE marking accordingly.