The importance of loudness normalization
With the rise of music streaming services, the term “volume normalization” is back in the spotlight. Music distribution platforms and streaming services that can be used in Japan have also announced the adoption of this “loudness normalization”, and discussions on this topic are becoming more active, especially among creators.
We spoke to David Shimamoto, who is actively spreading the word about studio engineering, what loudness in the first place means, and what loudness normalization means to audiophiles.
David Shimamoto, representative of Vocal-EDIT.com
David Shimamoto Vocal Editing Service Representative
Vocal-EDIT.com. Graduated from the Department of Music Technology / California Institute of the Arts. After working in USEN Corporation’s in-house SSL studio, he moved into the international video streaming business. After a dozen years, he returned to the world of music. The book “Tokubakku-The Story of Digital Studio”, which focuses on the subject of loudness and deals with the Yomoyama story related to mixing and mastering from a unique perspective, is a self-funded book, but it is a lecture in many colleges music and vocational schools, has been adopted and introduced as reference material on Nico Nico Douga’s official blog. Twitter ID: @gyokimae
■ “Loudness” that quantifies how people hear it.
Loudness normalization is a mechanism that standardizes the volume of content playback that was originally introduced by broadcasting stations in Europe and the United States. Specifications established by an industry group called EBU (European Broadcasting Union) / ITU (International Telecommunication Union) are currently used throughout the world. LUFS (Loudness Units Full Scale) is primarily used as a unit to express loudness (sometimes the unit called LKFS is used, but the meaning is almost the same).
In TV broadcast, if the volume differs depending on the content, such as commercials, dramas and music shows, it will cause annoyance to the viewer. Therefore, a certain standard was set as a request from the broadcasting station.
The normalization of loudness was originally born from the request for television broadcasting and is a mechanism devised to keep the perceived volume of various content constant.
First of all, “loudness” is a different concept from the mere volume and level of electrical signals. Since the human ear does not sound the same at all frequencies, the concept of “volume” was born as a method to reduce it quantitatively based on “how loud it can be heard by the human ear.”
Even at the same signal level, the human ear has the characteristic that low-frequency sounds are more difficult to hear, sounds are more audible around 4kHz, and continuous sounds are more audible than instantaneous ones. Loudness is a quantification of how music is heard based on these characteristics.
There is also the word “sound pressure” as a word with similar nuances. The original meaning of the word “sound pressure” is to express how much is greater than the minimum level that the human ear can perceive, with one unit of pressure. However, today, as the word “sound pressure warfare” represents it, there is a slight deviation in its meaning.
Therefore, based on the intention of Mr. Shimamoto in this document, we do not dare to use the word “sound pressure”, but we use two things: “signal level”, which indicates the magnitude of the digital signal, and “loudness”, which quantifies the hearing of the human ear. I want to try to explain in words.
(Since the method of calculating the loudness value is complicated, I will skip it here. To understand this article, I would like you to keep in mind that the higher the number, the louder the sound.)
■ Broadcast service The role of loudness normalization in
Listeners in general are rarely aware of the existence of loudness normalization when used as a broadcast application. However, with the launch of music streaming services, it has also become of great importance to music listeners. Specifically, the user can now configure the on / off in the application.
