Worship Musician August 2020 | Page 115

The broadcast industry inspired the development of the LUFS meter because of the growing increase in the loudness of advertisement audio compared to television program audio. INTRODUCING LUFS And to the rescue came Loudness Units relative to Full Scale (LUFS). LUFS equate the perceived loudness of one production with the perceived loudness of another. Designed for the broadcast industry, and established in 2011/2012, a LUFS meter facilitates loudness normalization. Most of us are familiar with peak normalization or level normalization, which adjusts the digital level of a waveform so that the peak levels all reach a maximum dBFS reading—often 0 dBFS, but several normalization plug-ins let the user select any maximum level. Loudness normalization is like level normalization in a way, but lets the user set a perceived loudness level for the audio waveform. RMS level—the level measured by a VU meter—provides an average level measured over a span of a few hundred milliseconds. It equates closer to perceived loudness and doesn’t contain peak readings. The beauty of the LUFS reading is that it measures the difference between the average (RMS) level and the peak level. It legitimately takes into account the peak and average levels. Upon much ponderance, most folks could see how the closer that average level gets to the peak level, the louder the audio will sound! The LUFS reading is in negative numbers and -12 LUFS simply indicates that the average perceived loudness is 12 dB below the peak level. So, given a common peak level of 0 dBFS, it makes sense that a waveform that reads -24 LUFS would sound a lot quieter than a waveform that reads -8 LUFS, even though both waveforms have the identical peak level! GET YER LUFS HERE! You might say, “Well Bill, how do I get me some o’ them LUFS?” At the root of the volume wars is the peak limiter. Peak limiters have a superfast attack time that’s capable of catching all of the transient content and keeping it from exceeding the threshold. It also has a fast release time so that it can recover quickly enough to stop the next transient. Peak limiters are different than normal compressors because there’s no practical need to adjust the attack or release time. Most peak limiters, such as the Waves L1, L2, and L3 Ultramaximizers, have two sliders: one that pushes the audio signal up into the threshold (essentially turning the average level up while increasingly limiting the peaks) and another that sets the peak level. Mastering engineers have been using peak limiters for a long time to set the mastered loudness level. There’s a lot more that goes into a great mastering job, but once everything else is set, the peak limiter is a tool that can help find the desired LUFS setting. Insert a LUFS meter at the end of your signal chain, just before the LUFS meter, and use the threshold of a peak limiter to push and pull the mix level to and from the threshold until you find the setting that results in your target LUFS reading. But there evolved a problem. Once musicians and engineers figured out that a peak limiter could help their music sound louder, it was like giving kids the keys to the candy shack! They stopped leaving it to chance—or to the discretion of an experienced and wise mastering engineer. Instead of leaving at least a few dB of headroom and trusting the mastering engineer to choose the perfect final processing, engineers and producers started to do their own backend processing. This caused mastering engineers to start complaining that, by the time they received the audio files, they were already way over limited. WHAT’S A TRUE PEAK? There’s another concern that accompanies loudness normalization called the true peak level. When your digital audio data is finally converted to analog audio waves (so the listener can hear it) the DAC redraws the waveform as smoothly as possible. If a few samples have clipped—or are legitimately all at 0 dBFS—the waveform is drawn with a rounding peak that exceeds 0 dBFS. This is called inter-sample distortion, and is problematic in that it isn’t visible on the final output on a dBFS meter but it needs to be dealt with because inter-sample distortion can overdrive consumer playback devices, causing them to distort, even though the dBFS meter doesn't show any clipping or overs. Most meters that read LUFS contain a True Peak meter that can read and limit theses problematic levels. Turn on the True Peak limiter and set it to limit these peaks at least by 1 dB True Peak (dBTP). Some mastering engineers and streaming services prefer to limit these peaks by 2 or 3 dBTP. It’s also important to note that these True Peaks aren’t necessarily caused by audio data that is corrupt or distorted, so simply lowering the level or the digital to analog bounce by 1–3 dB could solve the problem; however, this fundamental adjustment would also affect the perceived loudness of the file. Most engineers prefer to provide their best mix and limit the True Peaks in the final stage of mastering. HOW MANY LUFS ENOUGH Okay, I know, you’re probably saying, “Bill. O.M.G.! I get it! LUFS might be the single most important audio topic of 2020! HOW MANY August 2020 Subscribe for Free... 115