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  • Writer's pictureMatthew Losey

dB vs RMS vs LUFS in Broadcast Audio | How-to #12

Updated: May 2, 2023

Introduction

Broadcast audio quality is a critical aspect of any church production, whether it be for radio, television, or most commonly, online streaming platforms. Poor audio quality can be a major distraction for viewers or listeners, and can even lead to disengagement from the content being presented. Therefore, it is essential to understand the different elements that contribute to high-quality broadcast audio.

dB (decibels), RMS, and LUFS (Loudness Units Full Scale) are all important terms to know when it comes to understanding broadcast audio. Decibels are the most basic unit of measurement for the intensity of sound and are commonly used and referenced next to the input faders. Loudness refers to the subjective perception of the intensity of sound, which can vary depending on a person's listening medium, speakers or reference understanding. RMS, or root mean square, is a measure of the average power of a signal across the spectrum of the decibel measurement within an audio board or software. LUFS is a measurement of loudness that takes into account the entire duration of an audio signal, rather than just a momentary peak, as decibels, or RMS might focus on.

Having a solid understanding of these terms can help church audio engineers ensure that their broadcast audio is of the highest quality possible, but almost more importantly, least distracting as possible. By taking into account factors such as LUFS and not just decibel readings, engineers can facilitate online church environments that are not only clear and engaging but also comfortable to listen to for extended periods of time. High-quality broadcast audio for church experiences has never been more essential.

dBs vs RMS vs LUFS

When it comes to understanding broadcast audio, it is important to know the difference between decibels, loudness, and RMS. Decibels, or dB, are a unit of measurement used to quantify the loudness or amplitude of a sound. This means that dB is a measurement of the volume of the sound, and it is often used to describe how loud a sound is compared to a standard reference level. In broadcast audio, dB is commonly used to measure peak levels and to ensure that the audio signal is not distorted or clipped.

Think of it in terms of the peak light that is seen, the highest point of that light, is considered the decibel reading. The interesting thing to note here is that light is just a peak reference for the spectrum of audio that is also within that channel. That is why EQ, or equalization, exists. There are an infinite number of decibel readings across the frequency spectrum from 20Hz to 20KHz. Sometimes your peak is on the low end, maybe 400hz, and other times your peak may actually be from 3,000 Hz. Generally, when you’re looking only at the input level, you only care about the loudest point though so you can set your gain staging.

Loudness, on the other hand, is a subjective perception of sound that varies depending on the listener. It refers to how the human ear perceives the volume of a sound, and it can be affected by a variety of factors such as frequency, duration, and background noise. In broadcast audio, loudness is often measured using a standardized system called LUFS, which takes into account how the human ear perceives loudness and provides a more accurate representation of the perceived loudness of the audio. It is a very clever and somewhat recent measuring tool to have.

RMS, or Root Mean Square, is a mathematical calculation that measures the average power of an audio signal. In broadcast audio, RMS is often used to measure the overall volume of a signal and to ensure that the audio is properly balanced. Unlike dB, which measures the peak level of a signal, RMS takes into account the entire waveform of the audio signal and provides a more accurate representation of its overall volume. RMS was one of the early attempts to accurately quantify the loudness of a signal before LUFS standards were introduced.

LUFS in Practicality

In broadcast audio, loudness normalization is a crucial process that ensures a consistent and enjoyable listening experience for audiences. One of the best primary tools used for this purpose is Loudness Units Full Scale, which measures the perceived loudness of audio content in a standardized manner. Unlike traditional decibel peak normalization, which only considers the maximum volume level of the audio, LUFS takes into account the average loudness over time, providing a more accurate representation of how loud the audio actually sounds to listeners.

LUFS is widely used in broadcast audio, particularly in streaming platforms and television, to ensure that audio levels are consistent across different programs, channels, and devices. By using LUFS, broadcasters can prevent jarring shifts in loudness between video channels, and videos within the channel.

Using LUFS in broadcast audio has several benefits compared to traditional peak normalization. Firstly, it provides a more accurate representation of the perceived loudness of the audio, taking into account factors such as the frequency balance, dynamics, and duration of the content. This enables audio engineers to ensure that the audio sounds consistent and natural across different programs and platforms, regardless of the maximum volume level. Additionally, LUFS allows for greater flexibility in audio mixing and mastering, as it enables engineers to focus on the creative aspects of the audio rather than simply maximizing the peak level.

Standardizing using LUFS minimizes the need for manual volume adjustments during the broadcast because the engineer can make those changes and create figurative bowling bumper rails beforehand through clever compression and dynamic audio mastering. Overall this provides a more pleasant and consistent audio experience for viewers and listeners. While LUFS measurements are actually regulated for television broadcasters, churches don’t need to be worried about any such regulation on the internet. But even though it is not a regulated area, it can be helpful to apply best practices and standards within your own organization to emulate successful ones to break down the first initial audience barrier of not being respected because of poor audio quality.

Tools:

Depending on your country and your preferences -14 LUFS is the target for audio. Here are several options for LUFS metering for software solutions as well as hardware solutions for larger operations and live productions.

Free Software Plugins:

Paid (much better) Software Plugins:

Hardware Solutions:

Conclusion (TLDR):

  • LUFS provides a more accurate representation of perceived loudness.

  • LUFS is king for loudness measure reference.

  • Aim for -14 LUFS when mixing for your online audience.

  • Use a constant reference in the form of software or hardware to aid you.

All I am trying to do is introduce new language to help you equip your team for success. Now that you have the language for referencing loudness instead of only having to rely on peak mastering of the dBs, you can have a more holistic understanding of that one representation for volume in general. Now you can actively work to have a consistent and excellent audio in the moment instead of finding out later. The next missing piece to consistent audio in your mixes is the application of proper utilization of compression. Happy mixing!


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