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Audio Levels and Metering: Part 2

Written for Aotg.com by Michael Cardillo
Michael's Site: michaelcardillo.com/soundmind/
Sound for Editors: Soundforeditors.com
Twitter: @michaelaudio

If you haven't read part one: Read it here

Probably the most frequent question I get from editors is about a target level for their audio mix. I hear numbers such as 0 dB, -6, -18, etc., which typically refer to dBFS (decibels relative to full scale) as reflected on the built-in Peak Program Meters (PPM) in their NLE. These meters tell you how much headroom you have, which is how close your highest peaks are to digital distortion. This peak value has very little to do with the average level, or the perceived loudness, and as such, is not too useful in finding that "target" mix level.

Types of Meters:

1. PPM (Peak Program Meter) - the most common digital audio meter. Only displays 
instantaneous peaks (in dBFS) and has no loudness reference.

2. VU (Volume Unit) - based on analog signal flow, with an optimal target of 0 VU. Gives 
better indication of loudness than PPM, based on audio energy, but not standard in 
today's digital workflow.

3. Dorrough - also based on audio energy, displays both average and peak levels. 
Excellent tool for mixing, but does not give LKFS reading, per CALM Act.

4. CALM Act meters (various) - come in all shapes and functionality. All will give 
separate readings for True Peak and Loudness. They measure short term and long term (duration of the program) as well as a Loudness Range. There is a great deal of science that goes into calculating both True Peak and Loudness, but to simplify:

a.True Peak measures peak levels even if they come between samples (your NLE's PPM will not), and may read higher than traditional peak metering.

b. LUFS (Loudness Units Full Scale) and LKFS (Loudness K­weighted Full Scale) are just two different ways to refer to the same scale and the number is still in decibels (dB) relative to full scale. New Loudness measuring techniques take into account many factors in order to establish standards for measuring and mixing. click for more detail on ATSC A/85 and BS.1770

In this video, I demonstrate how get a basic mix with proper metering. I use clip gain as well as track volume and explain the difference. In the "uncut" version of the video, I go into more detail and also use EQ and compression to improve clarity of the mix, while maintaining the target mix levels.

For this demonstration, I mix a 60-­second teaser from unmixed stems. The music is full scale, which is representative of any CD or library music you might use. The mix objectives are to balance the music against the soundbites and land at -­18 dB LKFS for a web video mix, keeping in mind that the LKFS reading is for the duration of the program.

Then I export at ­-24 for broadcast using iZotope Loudness Control.

For anyone interested in viewing the entire mix process, the "uncut" version is 25 minutes and includes more detail throughout, as well as some compression and EQ.

In the process of preparing this article and video, I discovered a plugin meter called Insight from iZotope. I already own it as a part of RX4 Advanced, so I decided to check it out. It turns out that this meter is the one-stop shop I may have been looking for.

Two things you need to know about your audio level are: 1) what spec you would like to hit for your particular deliverable; and 2) how to monitor and control both average levels and peaks. I hope this article and video were helpful in getting you there. Thanks for reading.

More about ATSC A/85 and BS.1770

ATSC (Advanced Television Systems Committee) released a recommended practice in 2009 to establish and maintain audio loudness for digital television (ATSC A/85). This document also introduced BS.1770 as a standard of weighted measurement, which uses more than just sound energy information in calculating perceived loudness. If your meter offers both as separate settings, they should read about the same, depending on your content. If you don't know which one to use, I would choose BS.177-­3. Go back to the what you were reading

About the author

Michael Cardillo is an independent sound designer and audio post production mixer in the Atlanta area. He also writes articles and blogs for editors on the subject of sound and is currently in the process of co-writing a book on that subject with editor Kylee Wall. Information on the upcoming book can be found at soundforeditors.com

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