Friday, June 23, 2017 23:06
Logic’s “Loudness Meter”
Maybe you already stumbled over the Loudness Meter plugin in Logic’s Audio Effects Plugin Menu under the Metering section and was wondering, “what the heck is that?”. I will explain, not only how it works and how to use it, but also dive into the whole topic about Loudness Normalization to provide some background information so you understand why you should have this Loudness Meter on your Output Channel Strip all the time during your mix.
Rules and Regulations
There are various national and international organizations (ITU, EBU, AES, SMPTE, etc.) that have some brilliant minds who studied loudness and came up with suggestions and recommendations for how to use and implement technology based on their research that often make it into government regulations and laws, so radio and television, overseen by the government, have to follow. In addition, private companies have adopted various recommendations for their popular apps, like YouTube, iTunes, Spotify, or SoundCloud and this is where you seriously have to pay attention to when your mixes make it out of your studio and onto any of those listening channels, because, all of a sudden, your bounced mix might sound differently.
About the Basics
Before learning about WHAT happens to your mix after it “leaves” your Logic Pro X project and reaches your listeners, you have to be aware of WHY it happens. What is the problem? Let’s start with a few basics.
Listening to your Song(s)
Whenever you want to listen to a song, regardless whether it is on your computer, CD-Player, car radio, etc., you set the playback volume to your liking, and that’s it. Chances are, you don’t have to touch the volume knob while listening to that one song. You determine your own “Playback Volume”. However, if you now listen to a second song, you might have to change that Playback Volume by turning the knob up or down if you “feel” that the second song is too loud or not loud enough compared to the first song. The important word here is “feel” because it is a subjective decision to change the volume based on how you perceive the loudness. Please note that turning down the Volume Fader on your Output Channel during the mix, on the other hand, is an objective decision, for example, if the red clipping LED tells you that it reached 0dBFS.
Terminology: Level - Volume - Loudness
The previous paragraph had a few terms we need to pay attention to before going on any further. Although most users know these terms, they could mean the same thing or different things, depending on who is using the term and in what context.
- Level: In audio production, this generic term describes the audio signal strength. The Level is something that you measure, usually with a Level Meter that you find on Logic’s channel strip or as a separate “Level Meter” plugin.
- Volume: The term “Volume” is often used the same as “Level”. For example, does the Volume Fader on the channel strip change the “volume” or the “level”? You pretty much can use both terms.
- Loudness: If you increase the Volume Fader, you raise the Level on that Track, so the signal gets louder. That means, you also increase the loudness. But what is “Loudness” exactly? Here you have to pay attention.
What is Loudness?
Because in this article we talk about “Loudness Normalization”, we have to be clear about what the term “Loudness” refers to. If we consult the “Book of Knowledge”, Wikipedia, we find the following explanations:
“Loudness is the characteristic of a sound that is primarily a psycho-physiological correlate of physical strength (amplitude)” - or how about this - “That attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud”. Any questions?
Let me try to explain it differently:
The term “Perceived Loudness” is especially important when listening to a sequence of songs and you determine if you feel that all the played songs have about the same loudness or if you feel the need to turn the playback volume up or down for a specific song or part of the program you are listening to (on the radio or TV) to achieve some consistency of their playback level.
Although the Perceived Loudness is subjective, there are also meters that can measure loudness. However, you have to pay attention, because there are two types of Loudness Meters. I will go into more details throughout this article, but here is just the short explanation:
- RMS Meter and VU Meter: A Peak Meter that you can set to RMS (“Root Means Square”, a fancy word for “average”) or a traditional VU Meter is technically still Level Meters and not Loudness Meters. They measure the electrical level of an audio signal. However, their characteristics just happen to be close to how we perceive loudness by measuring and displaying the average signal level (or the energy of the signal) instead of the peak level of a signal. Also, keep in mind that an RMS Meter can read the average level but not a long-term average as the Integrated Loudness Meter can (more on that later).
- Loudness Meter: A true “Loudness Meter” (like the the one we have in Logic Pro X) still measures the audio signal, but it uses standardized algorithms and filters (based on psychoacoustic models) to represent the actual perceived loudness of humans.
A Potential Loudness Mess
To better understand the standards and regulations, in our case “Loudness Normalization”, you have to understand the reason why it was necessary to create and enforce them in the first place. If you haven’t noticed, our audio production landscape got a little bit out of hand over the years (since the beginning of the digital audio revolution) when it comes to signal levels.
Different Audio Content with Different Loudness
As I already mentioned in the beginning, the problem regarding loudness could happen when you listen to a sequence of audio content, most likely from different sources when those individual sources (songs, commercials, interviews, TV-shows, etc.) have a different perceived loudness.
Here are a few examples:
- Listening to Audio Streaming Services: Not only can the loudness be different between tracks on streaming services like Spotify, SoundCloud, or YouTube, the overall level when switching between services can also differ quite a lot.
- Listening to Radio: The jump in loudness between songs (and commercials) is replaced by a much bigger problem described as “Loudness War”, one of the reasons why Loudness Normalization standards where implemented, as we will see later.
- Listening to Playlists: If you listen to your iTunes Playlist with songs from different CDs or downloads (and even your own mixes), then the loudness of various songs can be quite different, especially if you listen to original records from the 70s and 80s (not the “re-mastered” ones) compared to recent recordings.
- Listening (watching) TV: Broadcast TV was always a nuisance when the different loudness of the commercials compared the show let you jump up to reach for the volume control. The complain from listeners over the years pressured the lawmakers to pass legislations that forced broadcasters to implement standards surrounding the Loudness Normalizations. For example, in the US, the CALM Act (Commercial Advertisement Loudness Mitigation Act) prohibits since 2012 under penalty to play TV ads louder than the regular program.
Who’s to Blame
So what are the factors that the perceived loudness of different audio recordings varies so much? Here are the three main components, “Peak Level”, “Dynamic Range”, and “Frequency Content”. Think about it; these are all elements that you control in your mix. So, as we will see, proper Loudness Normalization starts already during your mix, and it should be on your mind at that stage, way before you start bouncing your final mix or hand it over to the mastering engineer whose duties are, otherwise, reduced to damage control.
-1- Peak Level
But if all audio files (songs, commercials, interviews, etc.) are “normalized to 0dBFS”, which means the highest level of each audio files is 0dBFS, then isn’t that a good standard? As an “electrical standard” maybe, but it is completely useless (irrelevant) for the loudness, because Peak Level has nothing to do with how our ears perceive loudness and, therefore, the perceived loudness of each song in a sequence (all normalized to 0dBFS) could still be quite different, depending on other factors, especially the dynamic range.
-2- Dynamic Range
The Dynamic Range of a song describes the variation of the peak levels throughout the song. For example, is your peak meter constantly pressed against the maximum level or is it fluctuating between different levels with quieter parts, louder parts, and plenty room for transients?
The perceived loudness of a song increases when the song has less dynamic. Unfortunately, producers and record companies used that to game the system by compressing their song more and more and, therefore, making their songs sound louder compared to other songs when played on the radio (because “louder sounds better”). Pretty soon, everybody started to use that same technique, using less and less dynamics, and the “Loudness War” was in full swing with major casualties, good sounding records. More about that later.
-3- Frequency Content
That frequency content is important for the perceived loudness because it has to do with the frequency response of our ear. The so-called “Equal-Loudness Contours” (a revision of the famous “Fletcher-Munson Curves”) shows that our ear is much more sensitive to frequencies around 3kHz and less sensitive to frequencies above and even less sensitive in the lower frequency range.
That means an audio signal with 3kHz playing at 0dB sounds much louder than an audio signal with 100Hz normalized to the same 0dB level. Also, the sensitivity changes (the shape of the curve), depending on the playback volume.
You can see that the Loudness Contours are getting flatter with higher playback volumes (y-axis). That’s one of the reasons why “louder sounds better”, because when you increase the playback volume of a song, the ear’s perception is that the lower and higher frequencies will increase more compared to the 3kHz range, making the same song sound better due to the wider frequency range).
Subjective Loudness Measurement
A Broken System
As I already mentioned that we are facing a few challenges when listening to songs or any audio program on broadcasts or streaming services, and even our own iTunes Playlists:
- The audio material often has different perceived loudness that requires to manual adjust the playback volume throughout the program.
- Standard Level Meters only measure electrical signals and won’t reflect the characteristic of our ears based on perceived loudness.
- Peak Normalization to 0dBFS is only a technical standard that doesn’t relate how we perceive loudness.
- The Loudness Wars make matters even worse because it results in sound degradation, or in other words, shitty sounding mixes when overly compressed.
How to fix the System
The first step in fixing the problem is to come up with a method for Subjective Loudness Measurement. This is nothing new, and in the past, different proposals and implementations were trying to tackle that problem:
- VU Meter and RMS Meter: This is the traditional method of reading the average signal levels which happen to be close to perceived loudness.
- ReplayGain: This was a standard proposed by David Robinson in 2001 that is still implemented in some audio players. https://en.wikipedia.org/wiki/ReplayGain
- K-System: Proposed by renowned mixing and mastering engineer Bob Katz, this is a studio monitoring calibration system combined with special level metering to achieve a consistent dynamic range http://www.aes.org/technical/documentDownloads.cfm?docID=65
- ITU-R BS.1770: This is the title of the now global standard for the so-called “Loudness Normalization”. It is implemented by broadcast systems in many countries and adopted in some variations by most of the online streaming services.
The New Concept - “Loudness Normalization”
The major achievement of the new Loudness Normalization standard is that brilliant engineers found a method of how to measure Perceived Loudness with special “Loudness Meters” and establishing a “Target Level” that the audio program is referenced to. That means, a shift from Peak Normalization to Loudness Normalization, so all audio is normalized (referenced) to that Target Level and, therefore, establishing a consistent Perceived Loudness for the listeners throughout different audio material.
Peak Normalization vs Loudness Normalization
Before getting into the details about Loudness Normalization, here are three simple diagrams (inspired by Florian Camerer’s entertaining AES presentation from 2011), that demonstrate the concept of Loudness Normalization compared to Peak Normalization.
The different items in the diagram represent various audio files with different dynamics. With Peak Normalization all those files are moved up to the red line to have the same 0dBFS Peak Level (red dot). The green dots represent the individual loudness of the various files based on their different dynamics and, therefore, the different perceived loudness that varies when playing the audio material in sequence. That means you have to adjust the playback volume.
To compensate for the loudness variation, you could compress the audio files (as many radio stations do) to achieve a more consistent loudness. However, this would affect the quality of the individual audio files, especially if the compression is automated based on a single generic setting.
➌ Loudness Normalization
- Program Loudness: Each audio file (song, commercial, TV Show, etc.) is analyzed to determine its individual loudness, the so-called Program Loudness (green dot).
- Target Level: The broadcaster, streaming service, and even your iTunes app sets a fixed Target Level (green line) that the Program Loudness level (green dot) of each individual audio file is aligned to, the procedure called “Loudness Normalization”.
- Peak Level: An absolute Peak Level (red line) is still maintained to prevent clipping above 0dBFS.
As you can see, each audio material is played back with its original dynamics at a playback level that ensures that every song has a similar loudness. By setting the Target Level pretty low (-16LUFS … -24LUFS), the system has enough headroom before clipping to allow the playback of dynamic audio material and ends the urge to produce hyper-compressed mixes.
Basic Loudness Normalization Procedure
Here is the simplified procedure how Loudness Normalization works in action. This is the crucial part to understand because it shows you how you should mix your song, and more importantly, how not to mix your song to avoid being “punished” and played back at a lower level than other songs.
I explain the unit “LUFS” (Loudness Unit, referenced to Full Scale) in a moment, but for now, think of it as of the regular dB scale (1 LU = 1 dB, 0 LUFS = 0 dBFS).
#1 - Target Level
A system (broadcaster, streaming service, personal music player, etc.) that uses Loudness Normalization sets its Target Level (-14LUFS … -23LUFS). This is the Loudness reference that all the audio material played on that system is aligned to. Remember, "the good thing about standards is that there are so many of them". This is also true for the Target Level. European broadcast systems use a Target Level of -23LUFS, America uses -24LUFS, and most audio streaming services use a higher Target Level close to the AES recommended -16LUFS.
#2 - Measuring individual Program Loudness
Any audio material (songs, commercials, long-form shows, etc.) that is played on the system is first analyzed to determine their individual Program Loudness (different procedure for live broadcasts). That means, for example, the signal level of a song is measured from the beginning to the end with a standardized Loudness Meter, to find the integrated “Program Loudness” for that specific song. For example, -10LUFS.
#3 - Apply Gain Offset
When a song is played on a Loudness Normalized system, it looks at the Program Loudness for that particular song and raises or lowers the level to adjust the Program Loudness of that song to the Target Level of the system.
A few thing to be aware of:
- The song itself is not processed, only a gain offset is applied if required.
- If the Target Level of the system (i.e. iTunes) is -16LUFS, then a song with a Program Loudness of -18LUFS is raised by 2dB and song a with a Program Loudness of -14LUFS is lowered by 2dB.
- Only a song with the Program Loudness of -16LUFS plays back without any applied level offset.
- A highly compressed song, resulting in a high Program Loudness of -4LUFS, will be played back on that system 12dB lower and ends up having the same perceived loudness as a track with a healthy dynamic. The hyper-compressed track just might sound worse due to its distortion and lack of transients and nuances.
#4 - Prevent Clipping
The system still checks the absolute level of a song to avoid any clipping. For example, an individual song with a low Program Loudness will not be raised to the Target Level and only as much so the Peak Level of that song would not go over 0dBFS of the system. See the Peak to Loudness Ration (PLR) below.
#5 - Compress (optional)
The Loudness Normalization standard also defines a dynamic range value of a song ("LU Range"). A broadcast system has the option to use this information to compress the audio material if it is necessary to comply to a specific dynamic of the transmitting channel or program.
The ITU (International Telecommunication Union) was the first international body in 2006 that came up with a tool to objectively measure the subjective Perceived Loudness of the human ear. It was published in the standard named ITU-R BS.1770.
The EBU (European Broadcasting Union) later formed its own research group to extended the ITU-R BS.1770 standard and published their recommendation as EBU R128. Further revisions of the ITU-R BS.1770 standard adopted some of the EBU R128 recommendations.
The AES (Audio Engineering Society) published their own recommendation for Loudness Normalization for streaming audio in the paper AES TD1004.1.15-10.
The ATSC (Advanced Television System Committee) in the US published their paper known as ATSC A/85, the “Recommended Practice: Techniques for Establishing and Maintaining Audio Loudness for Digital Television”.
There are other national standards like the TR-B32 for Japan or the OP-59 for Australia. The individual streaming services like iTunes, Spotify, SoundCloud, YouTube, Tidel, Pandora, etc. don’t commit to any of the international standards (at least not publicly), but most of them have implemented Loudness Normalization standards, each choosing their own Target Loudness Levels.
Keep in mind that the topic of Loudness Normalization is a “moving target”, because commercial streaming services can change their implementation without necessarily announcing it to their users.
Now lets get a little bit into the details of Loudness Normalization to learn the terminology and everything around it to better understand how that system works and understand how to use Loudness Meters when you mix in Logic or any other DAW.
The ITU standard established a new unit, the LU “Loudness Unit”. This unit is similar to the dB units for signal levels; LU just indicates that it refers to the loudness level and not the signal level.
- Relative Loudness Unit [LU]: The difference of 1 LU is the same as 1 dB (raise by 1 LU means raise by 1 dB). “LU” can also be written as “LK”.
- Absolute Loudness Unit [LUFS]: LUFS, Loudness Unit, referred to full scale (which can be pronounced “loves”) is referenced to 0dBFS.
LUFS vs. LKFS
Please note that there is some inconsistency with the labeling. The European standard uses the unit “LUFS”, but ITU and the US use the unit “LKFS” (Loudness, K-Weighted, referenced to digital Full Scale). Both units are the same. The letter K is just an unfortunate choice, originally established by the ITU. It has nothing to do with the “K-System” proposed by Bob Katz, instead, it is referring to the so-called “K-Weighing Filter” that the Loudness Meter uses to measure Perceived Loudness.
The Program Loudness, as we discussed already, describes how loud a section is, no matter if that section is a 20s commercial, a 5-minutes song, or a 2-hour feature film. It is measured from the beginning to end of a section, determining its integrated average loudness, using the unit LUFS (Loudness Unit referenced to digital full scale).
Target Level (Target Loudness)
The Target Level (or Target Loudness) is the reference level of a system (broadcast, streaming service, playback app, etc) each song, commercial, or TV-show will be “normalized” to based on their individual Program Loudness.
True Peak Meter
In addition to the Loudness Level, you still have to consider the Peak Levels of an audio recording. The ITU-R BS.1770 standard defines a new method on how to measure peak levels. Instead of measuring Quasi-Peak with conventional “Sample Peak Meters”, it requires the use of True Peak Meters to determine the peak levels of the program. This is important not to introduce distortion due to clipping (during conversion or transmission).
True Peak Meters use (at least 4x) oversampling to detect inter-sample peaks. The standard defines a maximum allowed peak of -1 dBTP (or -2 dBTP for data-compressed material). The reason for the headroom is that True Peak Meters based on oversampling are still not perfect and can produce errors.
The Peak to Loudness Ratio is the difference between the maximum True Peak Level of a program and its Program Loudness (its integrated loudness). This is basically the headroom between True Peak and Program Loudness.
This value is important in a situation where, for example, the Program Loudness of a song is -20 LUFS and the True Peak is -1dBTP. In that case, the PLR is 19. If the Target Level of the streaming service, however, is -16LUFS, then you end up with three options:
- The song is clipping by 3 dB
- The song is turned down by 3dB
- The song is limited by 3 dB
Method to Measure Perceived Loudness
The most important step in Loudness Normalization was in 2006 when the ITU came up with a method on how to actually measure the subjective Perceived Loudness. At its core it uses a simple weighting filter, called the “K-Weighting Filter” that reflects the non-linear frequency response of the ear (see Equal-Loudness Contours).
Careful with the “K”
There are other types of filter curves (A-weighted, B-weighted, Z-weighted) mainly used for measuring sound pressure levels (dB SPL). Unfortunately, the ITU chose the letter “K” for this curve, and also uses it as the unit for the absolute loudness level “LKFS” (Loudness, K-Weighted, referenced to digital Full Scale). This can cause confusion with the “K-System” or “K-Metering”, the metering and monitoring concept proposed by Bob Katz. It is even more confusing because the K-System tries to tackle the same problem with loudness, but it is different from the Loudness Normalization based on ITU standard.
The Loudness Meter also uses a so-called Gating Method that improves the measurement of the Program Loudness for programs with high dynamic and sections of silence. It ignores the silent or very soft parts of the program, so it doesn’t push the average level (Program Loudness) down and ends up with being too loud when normalized to Target Level.
The system actually uses two Gates:
- The 10LU Gate follows the measured program and gates signals below 10LU.
- The 70LU Gate ignores the unwanted noise and also functions as an auto-start for the loudness measure. You can start the measurement, but it only reads the signal when it detects a proper signal level.
EBU-compliant Loudness Meters
The concept of measuring the Loudness Level based on EBU R128 can be applied to all areas of audio production, production, broadcast, transmission, archiving, etc.
Here are the main parameters and controls found on Loudness Meter:
- Target Level: A marker or color code lets you set the Target Loudness Level that you want to use.
- Integrated Loudness (I or or ILK): This is the meter that measures the actual Program Loudness. Unlike conventional meters, this one requires that you actually start and stop the measurement to determine the integrated average loudness measured during that time window (from the beginning to the end of the song). For this “stopwatch" functionality, most Loudness Meters provide some sort of Start and Stop buttons, or use autostart.
- Momentary Loudness (M or MLK): This meter displays the current level with a response time of 400ms. Please note that this is not as fast as a Peak Meter that has around 10ms response time. Unlike the Integrated Meter, this meter has no Gate, so you can see the actual level no mater how low it is.
- Short-term Loudness (S or SLK) : This meter displays the current level with a very slow response time of 3s similar to an RMS Meter. It is a “rolling 3s time window” that continuously displays the integrated loudness of the last 3 seconds of the currently played program. It also uses no gate mechanism.
- Loudness Range: The Loudness Range (“LU Range” or “LRA”) is usually a numeric display that shows the dynamics of the measured material (i.e. your song). Please note that this is not the raw dynamic range of a song from the lowest to the highest level. Instead, it measures the average dynamic, the "Statistical Loudness distribution by excluding extreme levels" (this was developed by TC Electronic and made available to the EBU to incorporate in the open EBU standard). The Loudness Range value is an indicator if any dynamic treatment of that program is required under specific circumstances (distribution platform, playback devices, etc.). For example, a radio station, limiting the program to a specific dynamic range.
- True Peak: Some Loudness Meters also have a True Peak Meter or numeric readout so you don’t have to open a separate True Peak Meter Plugin to avoid any clipping.
There are two scales for Loudness Meters.
- Absolute Loudness Scale (0 LUFS = 0 dBFS): The absolute scale reads like a standard Level Meter where the 0LUFS is the same as 0dBFS. You set the Target Level (i.e. -23 LUFS) with some type of marker or color code, and that is your reference during the metering.
- Relative Loudness Scale (0 LU = -23 LUFS): Most engineers are used to a 0dB mark as a reference when they follow the meters during recording or broadcasting. This relative scale takes that into account by setting the Target Level (-23LUFS or any other Target Level) to 0LU on the scale, so engineers don’t have to change their metering habits.
Advantage of the Loudness Meter
With the new Loudness Meter we now know three things about a program:
- What is the loudness (how loud it is?)
- What is the true peak level (highest absolute value)
- What is the dynamic of the program
Please note that a conventional Sample Peak Meter doesn’t provide any of that valuable information!
Logic’s Loudness Meter
After learning all the basics about Loudness and Loudness Metering, we are now well prepared to look at Logic’s own “Loudness Meter” to see how to use it in your mix.
Loudness Metering did first show up in Logic v10.2.1 as part of the MultiMeter, but in version 10.2.3 it added the new Loudness Meter as its own plugin as part of the Audio Effects Plugins ➊. There are plenty of third-party Loudness Meter available (hardware and software) from free to a couple of thousands of dollars, but as long as they are EBU-compliant meters, they all do pretty much the same as Logic’s Loudness Meter. More expensive ones just have more bells and whistles and some cool graphics to display the measurements. However, all share the same common parameters and controls.
The first step when using the Loudness Meter is to set the “Target Level” or “Target Loudness”, the loudness reference a system (radio, streaming service, etc.) uses for Loudness Normalization. Because there are different standards using a different value for that Target Level, you have to know what you are mixing or mastering your song (or any content) to. Radio and television broadcast use a lower Target Level of -23 LUFS (Europe) or -24 LUFS (US) and music streaming services use a higher Target Level of -16 LUFS or -14 LUFS.
Logic’s Loudness Meter lets you set the Target Level to the reference you need.
- The horizontal yellow line ➋ on the meter represents the Target Level.
- This Target Level indicator is just a visual reference (a guide) that changes the color of the individual meter from blue to yellow when going above that value. Both the meter bar and the numeric readout above change the color.
- Click the Target Level ➌ indicator, and the line lights up, displaying the current value ➍ of the Target Level next to the line.
- Click-drag the Target Level indicator to move it to the reference level you need (between -30 LUFS and 0 LUFS).
➊ Momentary Loudness - M
The first meter on the left displays the so-called “Momentary Loudness”, which displays loudness similar to a peak level meter.
- The M Meter has a relatively short response time of 400ms (compared to the 10ms response time of a Sample Peak Meter).
- Keep in mind that this level is measured through the special Loudness filters (“K-Weighting”).
- The meter has no hold function. Once you stop playback, the meter will reset.
- You can click on the numeric readout ➋ on top to reset the meter during playback
➌ Short-term Loudness - S
- The S Meter has a longer response time of 3s.
- Think of the measurement as a “rolling 3s time window”. It continuously displays the integrated loudness of the last 3 seconds of the currently played program.
- Remember that the S Meter (and the M Meter) don’t use the gate feature when measuring the signal.
- This meter also has no hold function. Once you stop playback, the display will reset.
- You can click on the numeric readout ➋ on top to reset the meter during playback.
- On a heavy compressed track, M and S Meter will display similar values.
➍ Integrated Loudness - I
This meter needs some getting used to at first because you have to manually start and stop the measurement.
- One of the two buttons at the bottom toggles between Start and Pause ➎. to start the measuring or pause it
- The Reset button ➏ resets the I-Meter ➍. Alternatively, you can also click on the numeric readout ➐ above.
- When you stop playback, the current value on the I-Meter remains visible. However, the meter automatically resets when you start playback again.
- The big numeric readout below the meter with the label “Integrated” ➑ is the same as the small numeric readout ➐ above the meter. Please note that only the small number changes its color to yellow, not the big number when you go above the Target Level.
➒ LU Range - LUR
The LU Range Meter only has a numeric readout at the bottom. Remember that this is not the raw dynamic range of a song from the lowest to the highest level. Instead, it measures the average dynamic, the "Statistical Loudness distribution by excluding extreme levels”.
- The Start-Pause-Reset buttons also affect the LU Range measurement, which means you have to manually start it. Clicking on the numeric I readout will also reset the LU Range
- Keep in mind that for a song with a healthy dynamic the value will go down throughout the song. On a highly compressed song, however, it stays at a small value throughout the song.
➎ Start / Pause and ➏ Reset Button
As I mentioned already, these two buttons let you start and stop the measurement of the Integrated Loudness and the LU Range.
➓ Vertical vs. Horizontal
From the View menu at the upper-right of the Plugin Window, you can choose to display the Loudness Meter vertically or horizontally.
Logic’s “MultiMeter” Plugin
Logic’s “MultiMeter” plugin also has a Loudness Meter built-in. The user interface is a little bit different with a few setting you have to pay attention to.
True Peak Meter
As we have just seen, the Loudness Meter Plugin itself doesn’t have a True Peak Level Meter, so you always have to have an additional plugin window open to monitor True Peak (which you should). The ITU and AES standards define a maximum True Peak Level of -1dBTP (and -2dBTP for data-compressed programs). The MultiMeter Plugin has the advantage that it displays a Loudness Meter and True Peak Meter.
- Please note that the Peak Level Meter has to be set to “True Peak” from the Level popup menu ➊.
- The Peak Meter on top indicates what setting you have chosen (i.e. “TP” ➋).
- The Peak Meter has its own Target Level Indicator ➌ that you can set to -1dBTP.
The Loudness Meter section is a little bit different:
- There is only a single meter bar, displaying the Momentary Loudness (LU-M) ➍
- You can set the Target Level Indicator ➎ on that meter bar.
- On top of the meter bar are two numeric readouts ➏ displaying the Integrated Loudness (LU-I and Short-term Loudness (LU-S).
- The Integrated Loudness will be measured when you start playback and doesn’t have a separate Start button.
- You can reset the Integrated Loudness by clicking on the LU-I value.
The View Menu ➐ in the upper-right corner of the Plugin Window lets’ you switch between three different views.
- Full ➑: This is the default, displaying all the available controls.
- Compact: This view hides the bottom section and displays only the Meters and the Analyzer (or Goniometer if it was selected before).
- Meters ➒: This view only displays the Meters: the Loudness Meter and the True Peak Meter (if it was selected in the Full View before). This is a great option to have both, the Loudness Meter and the True Peak Meters displayed in one small Plugin Window.
Other Loudness Meters
In addition to Logic’s (free) built-in Loudness Meter, there are lots of third-party Loudness Meters, software and hardware, ranging from free to a couple of thousand dollars. They all display the same standard parameters based on the EBU R128 specifications but often have additional features, preferences, or sophisticated graphics like histograms (showing the level over time) or radar-style meters (showing the loudness over time in a circular fashion).
Here are just a few Loudness Meters with their link to check them out if they fit your needs and budget.
NuGen Audio VisLM 2
TC Electronic LM1n, LM2n, LM6n
Waves WLM Meter Plus
RTW Loudness Tools
HOFA 4U Suite
Toneboosters EBU Meter
The EBU R128 defines two references for the maximum allowed True Peak Level. For PCM files it is -1 dBTP and for data-compressed audio (mp3, AAC, etc.) it is -2 dBTP. The reason for this extra dB is the nature of data-compression algorithms that could have some “side effects” regrading the peak levels.
Apple provides a little help in that regards with an Audio FX Plugin called “AURoundTripAAC” located in the Plugin Menu ➤ Audio Units ➤ Apple ➤ AURoundTripAAC. It simulates what specific data compression algorithms do to your mix. Not only does it measure the signal level after the (simulated) encoding in real time, it also lets you listen how your mix sounds “encoded”.
AAC Simulation + Loudness Meter
If you put the Loudness Meter Plugin ➊ after the AURoundTripAAC Plugin ➋, you could measure the Loudness and True Peak Level “after” the AAC encoding.
The interface of the AURoundTripAAC Plugin is pretty simple:
- Encoded Format ➌: You select from the popup menu on top which encoding format you want to simulate.
- Mode ➍: The two buttons below let you switch between Audition Mode and Listening Test Mode. Set to Audition for this purpose.
- Monitor ➎: The two buttons below let you A/B-switch between "Source" (without encoding) and "Encoded" (with encoding).
- Clip Indicator ➏: The two bars below light up red when the source signal or the encoded signal is clipping.
- Details ➐: The Details section below provides more details about the signal. It displays the maximum Sample Peak ➑ and Inter-sample Peak ➒ (True Peak) for the left and right channel of the Source and Encoded Signal, plus the count ➓ below to show how many times the signal hit the peak.
You can leave the Plugin in Encoded Mode if you want to hear "the encoded results" during the mix, but make sure to bypass the plugin when you bounce the mix!
I explain the Plugin in more detail in my book “Logic Pro X - Tips, Tricks, Secrets #2”.
Even with all the focus on loudness and dynamic, don’t forget to keep an eye on the peak levels of your song.
“Level Meter” Plugin
Put the “Level Meter” plugin on the Stereo Output Channel as the last Plugin (before or after the Loudness Meter) and always set it to True Peak ➊. The Level Meter has its own yellow Target Level Indicator ➋ that you can set to -1dBTP or -2dBTP depending on the standard you are delivering for.
“Adaptive Limiter” Plugin
Here is one little detail worth mentioning regarding True Peak. If you use a limiter on the Output Channel Strip, make sure that it also uses True Peak Detection ➌. You can find this valuable feature in more Limiter Plugins nowadays, including Logic’s own Adaptive Limiter.
Sometimes the setting is called “Oversampling” because that is the technique behind it to catch inter-sample peaks. BTW, the higher you Sample Rate you use for your Project (i.e. 192kHz), the fewer problems with inter-sample peaks in general.
If you want to check what Loudness Normalization does to your mix when your play it in the context of other songs, you can use your iTunes app on the Mac or your iPhone to check that.
The Playback Preferences in iTunes ➍ and the Settings for the Music app on iOS ➎ has a checkbox labeled “Sound Check”, which activates Loudness Normalization for all songs in your iTunes Library at a Target Level of -16 LUFS.
iTunes supposedly has an “Album Mode”, using a single Program Loudness when playing back the songs of an album and switches to individual Program Loudness when you are not in Album View or use Shuffle Mode (I haven’t verified that yet).
Online Loudness Analysis and Comparison Tool
Here is a great online tool that works in the web browser to analyze tracks regarding their loudness and plays them back with and without Loudness Normalization applied to them.
- Go to http://musictester.com/demo/
- You can drag any audio file onto the page, and it will be added to a temporary playlist (they claim that the songs are not uploaded, only analyzed).
- Each song appears as a row ➊ in the Playlist with the following information: Title, Maximum True Peak (TPk), Program Loudness (L) and Peak to Loudness Ratio (PLR). You can even sort by a specific column by clicking on its header ➋.
- The waveform display ➌ on top shows the currently selected track (row).
- The popup menu in the upper-right corner ➍ lets you choose to play back the songs unaltered or with Loudness Normalization applied to.
- You have the Play/Pause and Stop button ➎ to play the playlist, and you can also use the spacebar on your keyboard to step through the playlist during playback for direct comparison of the songs in your playlist.
What does Metallica and a Vacuum Cleaner have in Common?
The infamous “Loudness War” started when music producers and record companies, but also producers of radio and TV ads tried to get advantage over their competitor by using the phenomena
that to listeners, louder audio material sounds better. Because the digital domain has a precise maximum allowed signal level of 0 dBFS that everybody had to follow, they tried to game the system by using compressors and limiters to reduce the overall dynamic of their song or advertising. The perceived loudness of a song (or any audio material) increases the less dynamic the song has.
Like with any war, there were casualties, and in this case, it was good sounding music with healthy dynamics and natural transients. Instead, the result was a squashed dynamic of just a few dB with high distortion, resulting in an overall shitty sound (despite the fact that they were produced on the best and most expensive equipment). Unfortunately, that didn’t matter as long as the product made a lot of money with those tracks. The motto wasn’t “let’s make good sounding music” and instead “To the Edge of Distortion and Beyond”.
Don’t get me wrong, trying to create a “wall-of-sound”-type of music is ok if it is driven by the intention of the artist and not by the guy from the record company that attends a mastering session and tells the engineer to hyper-compress a track just for the sake of gaining financial advantage over a competitors product (remember, it is called “Music Business” for a reason).
Dynamic Range and the Sound of a Vacuum Cleaner
Thomas Lund, an engineer at Genelec, had a great presentation about the loudness topic at the recent AES convention in LA where he compared a song from a Metallica album to the recording of a vacuum cleaner. The measurement showed that the sound of a vacuum cleaner had a greater dynamic range than the recorded “music” of the Metallica track, squeezed to an unbearable 3dB!
If you listen to a typical Top 40 radio station, most of the station IDs, ads, and fillers between songs are so highly compressed with short music snippets, whooshes, and sound effects, that the sonic result is often similar to the sound of white noise at 0dB.
Stop the Insanity
Finally, this insanity comes to an end with the implementation of the Loudness Normalization.
A Metallica song and an old Van Halen song can both be peak-normalized to 0dBF. However, the "super-loud" Metallica song with a squashed dynamic of 2dB will be turned down and will sound much softer than the Van Halen song with much healthier dynamic range.
Loudness Normalization: A New and Better World
Where are we now?
Finally, the big question is, what Program Level should we aim for in our Loudness Meter when we mix our song or any other material? Due to the different standards, there is no simple answer to that, because it depends on various factors. Here are just a few considerations.
- •Because there is not only one single reference for the Target Level, find out the Target Level of the station or streaming service your song will be played on (see below).
•If it is practical, you can create (maximize) the mix/master of your song for specific distribution channels.
•As a general rule, broadcast systems use a lower Target Level of -23 LUFS or 24 LUFS, while audio streaming services use a higher Target Level around the recommended -16 LUFS.
•Keep in mind that this topic is still “developing”, which means that some systems start to adopt the Loudness Normalization or set their previous Target Levels to a lower (more generally accepted) level.
•Whatever you are mixing to, Loudness Normalization will always favor dynamic music (played back unchanged) over highly compressed music (which will have its playback level turned down).
A few considerations about the mastering process.
- Maybe it is about time stop thinking about a mastering engineer as someone who applies compression or limiting to your final mix. If that is what an engineer is advertising without any knowledge of Loudness Normalization, then look for someone else.
- A mastering engineer should be fully aware of all the topics around Loudness Normalization because that is important for the well-being of your song when it is played on the radio or streaming services.
- Don’t loose your sleep over whether or not you should already apply compression to your mix (and how much) before you submit it to the mastering engineer and how much headroom is the right headroom. First of all, apply whatever processing to your mix to make it sound as good as possible, but always keep the Loudness Meter in sight.
- If you mix/bounce your song (or any content) using a Loudness Meter with an appropriate Loudness (-23 LUFS or -16 LUFS), and not going over the recommended -2dBTP True Peak Level, then you are fine.
- Keep in mind that highly compressed mixes leave you with an irreversibly damaged dynamics that even a mastering engineer cannot fix.
Public radio and TV stations worldwide adopting already the regional Loudness standards and more and more commercial radio stations are catching on to help improve consistency throughout the program. With private companies, that is a little bit more difficult because not only do they not necessarily announce any adoption to a specific standard, they often cherry pick specific procedures and references and change or update them at their will. The result is still quite messy, but definitely much better as before, and it is getting better because that is where the industry is heading.
Here is a list of some of the current standards (June 2017). Keep in mind, some numbers are detected by users, and the individual implementation varies quite a bit.
- Most public Broadcasting (radio/TV): -23LUFS or -24LUFS
- Tidal: -18LUFS over AirPlay, on mobile devices and browser it will be -14LUFS. Normalization can be turned off by the user.
- iTunes Radio and iTunes app: -16LUFS
- Spotify: They have recently lowered the Target Level from -12LUFS to -14LUFS. It seems that the ads in the free version, however, are still not normalized.
- YouTube: -13LUFS, but it seems that not all program (like older content) is normalized yet and also, the softer program is not turned up to the Target Level.
- SoundCloud: Doesn’t seem to use Loudness Normalization yet. Let them know you want it.
- Pandora: Doesn’t seem to use Loudness Normalization yet. Let them know you want it.
Here are a few topics that I didn’t get into in this article, but they show that there is much more to consider when it comes to delivering a consistent audio program using Loudness Normalization.
- Album Mode: There are still some considerations regarding a so-called “Album Mode” that was used in the ReplayGain system. It allows to measure the Program Loudness of an entire album, so when played back, the individual songs of that album are not Loudness Normalized individually. This prevents that the playback level of a quieter song or in classical music albums is raised against a louder tracks on that album
- Surround: The various standards also include details how to handle multi-channel surround sound material. For example, the LFE channel (the “.1” in “5.1”) will not be measured, and the surround channels are lowered by 1.5dB when measuring the Program Loudness.
- Live Broadcast: Broadcasting live audio is, of course, different regarding the loudness because you cannot measure its Loudness in advance.
- Spoken Words: Audio material with spoken word or a combination of music and spoken words has to be handled differently than pure music channels.
Last but not Least
Now with the new awareness of Loudness, be careful when reading any publication about Loudness. “Loudness” is not a new term so that articles may talk about loudness used in a more general term or the context of VU Meter or RMS Meters and not in the context of the new Loudness Normalization standards.
Links and References
Florian Camerer: Loudnesszen
Thomas Lund: Loudness Wars, Part 1
LUFS Meter Explained
Thomas Lund: The Tipping Point
List of Loudness Tools
10 Things to know about EBU R 128
PRSS (Public Radio Satellite System) Audio Loudness Standards
EBU R128 Website
Dynamic Range Day
I hope this extensive article about Loudness Normalization helped you to be better prepared for the real world with your Logic mixes.
If you want to learn more about Logic Pro X or other software apps you might use (Final Cut Pro X, Pro Tools, etc.) check out the best-selling books in my Graphically Enhanced Manuals (GEM) series. They are all available as printed books (from Amazon), pdf files (from my website), and as interactive multi-touch iBooks (exclusively on Apple’s iBooks Store).
All links are on my website http://DingDingMusic.com/GEM
Thanks for your time and interest,