Leq(m) is used to measure the loudness of theatrical cinema adverts and trailers, the stuff that happens before the main feature. Leq(m) measures decibels averaged over time with a weighting curve that is more sensitive to annoyance frequencies: breaking glass, explosions, and other piercing sounds. This allows for trailers to have loud explosions with enough quiet parts to balance it out so as not to fatigue or annoy the audience. Leq(m) has some similarities to BS1770 loudness measurements like LUFS and LKFS.
LEQ(m) trailer TASA 85 dB loudness level #
“The TASA Standard” is an audio standard for motion picture trailer volume.
At any given time, the TASA Standard identifies a specific Leqm number as a recommended upper volume limit for trailers in order to bring the audio level of trailers closer to the features they precede. The current upper volume limit is Leq(m) 85 dB.
The TASA loudness standard says that a quiet trailer should have a normal dialogue level. A normal trailer dialogue level is often -20 Netflix loudness level.
LEQ(m) commercials SAWA 82 dB loudness level #
SAWA has standardized Cinema commercial production formats such as Sound in Cinema & the Digital Medium of Cinema
The current upper volume limit is Leq(m) 82 dB as per International Standard ISO 21727 (British Standard BS5550 7.2.4)
The sound mixes on commercials are often run through more limiters/compressors and have less dynamics than trailers and features.
TASA and SAWA approved Leq(m) meters: #
- For Atmos, 7.1, 5.1, and 2.0: Nugen VisLM
- For 2.0 and 5.1: Nugen VisLM, Waves WLM Plus, Dolby Media Meter, and Dolby DMU
Calibration at the Cinema #
Cinemas are calibrated to the SMPTE RP 200:2012 standard where a -20 dB RMS pink noise signal is measured to 85 dBc and the reference fader level is set to 0. This means a -20 dB pink noise signal is played out of a single front channel, the amplifier powering that speaker cluster is turned up until a sound pressure level meter (SPL) reads 85 dB. The process is repeated for each of the front speaker sets. The surround speakers are calibrated the same way, except to 83 dB. Playing a calibration signal at -20 dB means that there’s an extra 20 dB available per channel as “ headroom,” or loudness which can be accessed before the signal clips or distorts. This incredible dynamic range is how the audience can hear very quiet scenes where whispers or footsteps are audible as well as scenes like plane crashes where the sound is very loud.
There you have it. Leq-m is an averaging loudness measurement system, using 850ms windows with a CCIR weighting filter to measure the loudness of cinema adverts and trailers. Note that there is no loudness spec for the main feature film. Once you have a calibrated room to 85dB c weighted and you set the Dolby RMU Dolby 7, its completely up to you.
