There are two main methods for measuring signal level: peak and RMS. Peak is the highest (maximum) point or points of the signal level, while RMS is the average value of the signal level obtained over a certain period. Both peak and RMS measurements are used to determine the signal's amplitude. Until recently, when working in the digital domain, 'peak' values were generally always considered. To be even more specific, 'sample peak' measurements were used for signal level in the digital domain.
The purpose of using the sample peak measurement method was to prevent signal distortion by keeping the highest points in the signal at a certain level. As you know, dBFS (decibels Full Scale) is used in the digital domain, and the maximum level the signal can reach on this scale is 0 dBFS. Distortion begins after this point. For this reason, in measurements and level adjustments made with the sample peak method, the final level of the track (or program) has been kept around -0.2 dBFS for years. The landscape changed when Inter-sample peak (true peak) came into play.
Loudness
As I mentioned above, peak and RMS measurement methods are used to determine the signal's amplitude. On the other hand, there is also the concept of 'loudness', which is referred to as 'sesin gürlüğü' (the volume of sound) in Turkish. Loudness is very important because it is related to how we perceive the volume of sound. Roughly, we can say that amplitude is related to the signal, and loudness is related to human perception.
Let's take two different tracks. Let both of their peak points be set to -0.2 dBFS. Let's compress the dynamic range of the first track with a compressor and limiter. Let's not touch the second one, or apply much less compression compared to the first. When you play these two tracks to people, everyone will say that the first track is louder. In other words, the first track will sound more 'loud' to everyone.
For this reason, the music and recording industry has been struggling with the 'loudness war' for years: "I want my track to sound louder on CD and radio than other tracks!"
The same frustrating situation affected radio and television broadcasting for years. I don't think I need to mention how annoying it is to jump out of your seat and frantically press the volume button on the remote control to turn down the sound when a commercial interrupts a movie or program on TV.
LKFS and LUFS
This situation in radio and television broadcasts played a major role in conducting various research and developing new standards. As a result of these efforts, the LKFS (Loudness K-Weighted Full Scale) scale emerged, which measures the perceived loudness of sound.
LKFS was standardized by the ITU (International Telecommunication Union) as standard ITU-R BS.1770. LKFS was also used in the ATSC (Advanced Television Systems Committee) A/85 standard. On the other hand, the EBU (European Broadcasting Union) changed the name of LKFS to LUFS (Loudness Units Full Scale) because its name did not comply with their naming conventions and included it in their document titled R-128: Loudness Normalisation and Permitted Maximum Level of Audio Signals.
In a short time, radio and television broadcasts in Europe, the USA, and some other countries began to adjust levels according to the LKFS/LUFS scale, and the use of this scale even became law in some countries.
Consequently, the era of panicking and grabbing the remote to turn down the volume when a commercial comes on while watching TV in countries broadcasting according to this scale has ended.
What We Need to Know About LKFS and LUFS
The terms and concepts we need to know about LKFS, LUFS, and generally the measurements of the perceived volume (loudness) of sound can be listed as follows:
- LKFS
- LUFS
- LU
- LRA
- True Peak
LKFS (Loudness K-Weighted Full Scale), as I mentioned above, is a scale used for measuring loudness.
LUFS (Loudness Units Full Scale) is completely the same as LKFS. Only the names are different. LKFS is the name used by ITU and ATSC; LUFS is the name used by EBU.
The unit used for LKFS and LUFS is LU (Loudness Units). 1 LU is equal to 1 dB: 1 LU = 1 dB. The top level on this scale (just like in dBFS) is 0 dB, so the measurement levels are expressed with negative (-) values.
There is no standard or suggested value for Loudness Range (LRA). LRA varies according to the music genre and track structure in music, and according to the program content in broadcasting. Although there are differences, we can consider the LRA values of today's tracks to be in the range of 4-7 LU for rock, pop, and R&B; 3-6 LU for hip-hop and EDM; and 7-12 LU for acoustic genres. It is useful to state again that there are no standards for these values, they are not rules, and I only included them as examples. A large LRA value indicates that the track has a wide dynamic range, and a low value indicates that it has a narrow dynamic range.
The Importance of True Peak Value
True Peak is higher than the sample peak value. If the difference between true peak and sample peak is very small, it may not be audible whether the signal coming out of the speaker is distorted. On the other hand, if the difference is large, audible distortions may occur. Considering that we must convert the signal from digital to analog and send it to the speaker to hear it, the importance of the true peak measurement method emerges. There are many plug-ins produced by different companies for a True Peak Meter. Some of them are:
- Waves WLM Plus Loudness Meter
- Nugen Audio VisLM
- TBProAudio dpMeter 3
- Youlean Loudness Meter 2 Pro
- beDSP Audio Loudness Meter 5.1
Some companies also produce plug-ins for true peak limiting. These include:
- FabFilter Pro-L 2
- Nugen Audio ISL
- Avid Pro Limiter
- Universal Audio Sonnox Oxford Limiter V2
- TBProAudio FinalLoud
Additional information: Izotope Ozone, a popular mastering plug-in, also features true peak limiting.
Why LKFS and LUFS Are Important for Music
LKFS and LUFS are concepts that must be known not only in the broadcasting field but also by those working on music production because the reference levels of streaming services like Spotify, Apple Music, and YouTube are expressed in terms of LUFS.
Even if you are not mastering, I think it is very important to have knowledge about these scales, and more importantly, to have an idea of how tracks will sound at different levels on these scales. You can install a free LKFS/LUFS measurement plug-in and experiment for this.
Free Plugins
- Loudness Meter 2 (Youlean) / Mac: AU, AAX, VST | Win: AAX, VST
Youlean Loudness Meter 2 is a plug-in that measures mono, stereo, and 5.1 surround signals using the LUFS scale. It also measures the 'true peak' value in the signal. Youlean Loudness Meter 2, which complies with the ITU-R BS.1770 standard, has presets for all broadcasting standards around the world. The paid version also includes presets for streaming services like Spotify, Apple Music, YouTube, and Tidal. You can resize the window of Youlean Loudness Meter 2 as you wish. I think this is also an important feature.
- PianoVerb (PSP) / Mac: AU, AAX, RTAS, VST | Win: AAX, RTAS, VST
PianoVerb is not a reverb plug-in developed for piano... PianoVerb is a plug-in that uses the piano as a reverb. This is actually not a new technique. If the strings of the piano are not dampened, sound waves coming from other sources in the room or space vibrate the strings. When you microphone the piano strings and record these vibrations, you get a kind of reverb. PianoVerb is a plug-in developed based on this idea.
- Acqua Ochre Homebrew EQ (Acustica) / Mac: AU, AAX, VST | Win: AAX, VST
Acqua Ochre Homebrew is a parametric EQ plug-in. It divides the signal into three different frequency ranges: 'low' (35-315 Hz), 'mid' (315-2500 Hz), and 'high' (2500-22000 Hz). The Q value can be set between 0.5 and 4 for each range. +/-16 dB cut/boost is possible.
- VHL-3C Vintage High/Low Pass Filter (Black Rooster Audio) / Mac: AU, AAX, VST | Win: AAX, VST
VHL-3C Vintage High/Low Pass Filter, as the name suggests, is a low-cut and high-cut filter plug-in that emulates old analog passive filter designs.
- mvMeter (TBProAudio) / Mac: AU, AAX, VST | Win: AAX, VST
mvMeter is a signal meter with different measurement methods. You can use it in Peak, RMS, VU PPM, or EBU R128 modes. The notable feature here is, of course, that it can measure according to the EBU R128 standard. mvMeter has various channel options, including stereo, left, right, mid, and side channel. It has five different interface designs. Don't miss out!
- 4U+ DynamicTiltEQ (Hofa) / Mac: AU, VST | Win: VST
4U+ DynamicTiltEQ is a tilt EQ with a variable pivot point. You will immediately understand how it works by watching the short video below. If you wish, you can use the plug-in with the dynamic EQ feature by purchasing the optional dynamic module.
- Filterjam (AudioThing) / Mac: AU, AAX, VST | Win: AAX, VST
Filterjam is a multiband resonant filter that gives results similar to ring modulation. The input signal is split into four and summed or multiplied at the output according to the selected mode. It is possible to use Filterjam very gently or very aggressively.
- HoRNet Harmonics (HoRNet Plugins) Mac: AU, AAX, VST | Win: AAX, VST
HoRNet Harmonics, as the name suggests, is a harmonic shaper. Unlike similar ones, it allows you to decide which harmonic to process. The plug-in has ten harmonic generators whose amplitude and phase you can adjust. Thanks to this feature, it is possible to obtain much different and more interesting results with HoRNet Harmonics compared to other harmonic shaping plug-ins.
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