The volume we see in our DAW is different from the actual peak levels. Any signal above 0dBFS (decibels relative to full scale), which is considered the absolute ceiling in digital audio, can clip. We can push a mix up to -0.1 dBFS without clipping, right? Well, not quite. True peak limiters can help prevent clipping that we might not otherwise be aware of in this situation.
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What is true peak?
DAWs use what is referred to as a sample peak program meter to monitor volume. The highest level attainable in a digital system is 0dBFS, and the meters we see in our digital mixer display values in dBFS. Common sense tells us that we can prevent clipping, which results in audible distortion and other unpleasant-sounding things in our recordings, as long as we keep our maximum values at or below 0dBFS. It’s more complicated than that in reality.
An analog signal is converted during digital recording into a digital signal that is saved on the computer. The sample rate determines how many samples are taken per second to reproduce the analogue signal. The peak values of these samples as they exist in the digital world are measured by the dBFS meters in the DAW. They do not, however, reveal the actual peak levels.
There may be modest level changes as a digital signal is transformed into an analog one for playback during the D/A conversion process. The signal’s analogue reconstruction can actually peak considerably above the highest possible digital sample value. An inter-sample peak or a real peak is what we refer to when that occurs.
Because genuine peaks are invisible to standard meters and limiters, your finished mixes may contain audio that is louder than 0dBFS. You won’t hear it while playing back recordings in the studio using quality converters. But digital clipping could be noticeable once the file leaves the DAW and is played back on another person’s machine. Converting mixes to lossy formats like MP3 makes it even worse.
What is loudness?
Loudness is measured in LUFS (sometimes known as LKFS), and is always assessed over a period of time. It is sometimes more correctly referred to as “perceived” loudness or “apparent” loudness. The relative scale used by LUFS and decibels is the same. The integrated loudness of a program or music refers to its overall volume. When we refer to “loudness,” we frequently mean integrated loudness. Although LRA (also known as loudness range), short-term loudness, and momentary loudness exist, they are less significant than integrated loudness, therefore for the sake of this blog, you can assume I’m referring to integrated loudness.
The ATSC A/85 used for television in the USA, the EBU R-128 used in much of Europe, and numerous other loudness requirements are all based on the ITU BS. 1770 guideline, which is the international standard for measuring loudness. Different frequency ranges are weighted differently in BS. 1770 because it considers factors like the acoustic effects of the human skull. The EBU R-128 and ATSC A/85 both call for integrated loudness measurements of -23 LUFS and -24 LKFS, respectively. Programs should typically be blended according to these specifications before submission. Conversely, streaming services like Apple Music, Spotify, and others have objectives for loudness (-14 and -16, respectively), but the audio is normalized after submission. In essence, this means that you are free to upload audio that is as loud or as quiet as you’d like, provided that you are aware that loudness normalization and the encoding procedure will very probably change how it sounds.
How to use True Peak Limiter?
The majority of meters and limiters only display sample peaks, or the highest value of the digital samples that make up the analogue signal that was recorded. True peak values that happen after the digital signal is transformed back to an analog one are not taken into consideration by these.
By using real peak meters and/or true peak limiters, inter-sample clipping brought on by D/A conversion can be avoided with the least amount of effort. Inter-sample peak values can be displayed by a true peak meter, and they can be identified and prevented from clipping by a true peak limiter. It is typically a stringent requirement that the program be mixed to genuine peak levels—not simply sample peak levels—for post-production and broadcast loudness specifications.
Loudness specifications for music are less rigid, but it’s still a good idea to understand genuine peak levels and how, depending on where your mix is used, they could degrade it. Inter-sample peaks, according to some, are essentially undetectable. The so-called “loudness wars” have resulted in certain big hits being mastered between +1 and +3dBTP (decibel true peak). That is terribly distorted and loud! It’s ideal to master at 0dBTP for the optimum audio quality and listening experience.