About this Article
Written by: James Bunning
Written on: December 7th, 2016
Tags: lifestyle, computer engineering, music, sound engineering
Thumbnail by: London Guitar Academy/London Guitar Academy
About the Author
James Bunning was a student at the University of Southern California at the time this article was written.
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Volume XVIII Issue II > The Battle of Sound
Software models of hardware compressors are used to create dynamic range compression (Fig. 2). Figure 2(a) depicts the uncompressed audio of the 1976 hit “Rich Girl” by Hall and Oates. The lighter blue portion in the middle of the waveform represents the audio signal’s average level. The higher the vertical height of the waveform, the louder the sound. Figure 2(b) shows what the audio signal looks like after passing through the compressor. Notice how the compressor greatly reduces the level of the waveform’s loudest parts. Lastly, the painted-on look of Figure 2(c) exhibits the last and most important step of compression: boosting the entire audio signal back to the original peak level. Comparing the compressed version of “Rich Girl” in 2(c) to the uncompressed version in 2(a), we see that the compressor has noticeably reduced the difference between the loudest and quietest parts of the song, increasing the track’s average level.

Limits of Loudness in the Vinyl Era

Although dynamic range compression initially allowed sound engineers to make louder sounding recordings, the physical characteristics of vinyl records put a limit on how loud music producers could push audio. A vinyl record stores audio information via small V-shaped grooves cut into its surface and plays the audio back when a needle runs over those grooves. In order to play louder audio recordings without the needle jumping during playback, sound engineers needed to cut deeper grooves [3]. However, with only a limited amount of useable surface area per disc, increasing the size of the grooves for louder songs meant sacrificing how many songs could fit on the side of a record. As long-play (LP) records became more popular in the 1960s and 1970s and needed to hold more songs per side, duration won over loudness, and the average loudness of songs stayed relatively the same until the early 1980s [3]. The surface of these vinyls were occupied by V-shaped grooves, offering a visual explanation of the pressure to choose between duration and loudness (Fig. 3).
Figure 3: V-shaped vinyl grooves.