Loudness (LKFS)

LKFS is an acronym that stands for “Loudness, K-weighted, relative to Full Scale.”

This term became part of the TV spot production vocabulary with a well-known broadcast law called the Commercial Advertisement Loudness Mitigation Act (or CALM Act), which is a set of rules adopted by the FCC requiring commercials to have the same average volume as the programs they accompany. These rules became effective on December 13, 2012, one year after the date of their adoption. Many advertisers are already familiar with the CALM Act, but not many fully understand LKFS.

Essentially, LKFS is a scale used to measure and compare the loudness levels of audio. Loudness cannot be measured using program or VU (volume unit) meters typically found in a production suite, as it is measured across the entire length of a spot. Measurement samples are made many times a second, then integrated and processed to produce the LKFS value for the spot. For delivery of content, the Target Loudness value should be -24 LKFS.

For advertisers, LKFS comes down to a simple matter of dollars and cents. Despite spending thousands of dollars to get commercials ready for air, some advertisers still run into complications with the broadcasters when their spot is not -24 LKFS. When the audio gets mixed for your spot, consider asking your team if it’s at -24 LKFS.

While the target is -24 LKFS, the CALM Act specs indicate that minor measurement variations of up to approximately plus or minus two decibels are anticipated and are acceptable.

Some producers misunderstand the ±2 dB thinking that they can produce a spot that is -22 LKFS while others understand the spec but choose to target the high side so that their spots sound louder than others – either way, the spec clearly says that content loudness should not be targeted to the high or low side of this range.

Extreme Reach will automatically normalize all spots to -24 LKFS but if a spot gets delivered to a broadcaster outside of -24 LKFS, most broadcasters will automatically normalize it to -24 LKFS while some will reject a spot that is outside the spec.

The next time you’re in post-production, it’s worth checking with your audio mixing partners about LKFS. Doing so can save you significant time, stress and money down the line.

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