Fade (audio engineering)
In audio engineering, a fade is a gradual increase or decrease in the level of an audio signal. The term can also be used for film cinematography or theatre lighting in much the same way and fade.
In sound recording and reproduction, a song may be gradually reduced to silence at its end, or may gradually increase from silence at the beginning. Fading-out can serve as a recording solution for pieces of music that contain no obvious ending. Quick fade-ins and -outs can also be used to change the characteristics of a sound, such as to soften the attack in vocal plosives and percussion sounds.
Professional turntablists and DJs in hip hop music use faders on a DJ mixer, notably the horizontal crossfader, in a rapid fashion while simultaneously manipulating two or more record players to create scratching and develop beats. Club DJs in house music and techno use DJ mixers, two or more sound sources along with a skill called beatmatching to make seamless dance mixes for dancers at raves, nightclubs and dance parties.
History
Origins and examples
Possibly the earliest example of a fade-out ending can be heard in Joseph Haydn's Symphony No. 45, nicknamed the "Farewell" Symphony on account of the fade-out ending. The symphony which was written in 1772 used this device as a way of courteously asking Haydn's patron Prince Nikolaus Esterházy, to whom the symphony was dedicated, to allow the musicians to return home after a longer than expected stay. This was expressed by the players extinguishing their stand candles and leaving the stage one by one during the final adagio movement of the symphony, leaving only two muted violins playing. Esterházy appears to have understood the message, allowing the musicians to leave.Gustav Holst's "Neptune, the mystic", part of the orchestral suite The Planets written between 1914 and 1916, is another early example of music having a fade-out ending during performance. Holst stipulates that the women's choruses are "to be placed in an adjoining room, the door of which is to be left open until the last bar of the piece, when it is to be slowly and silently closed", and that the final bar is "to be repeated until the sound is lost in the distance". Although commonplace today, the effect bewitched audiences in the era before widespread recorded sound—after the initial 1918 run-through, Holst's daughter Imogen remarked that the ending was "unforgettable, with its hidden chorus of women's voices growing fainter and fainter ... until the imagination knew no difference between sound and silence".
The technique of ending a spoken or musical recording by fading out the sound goes back to the earliest days of recording. In the era of mechanical recording, this could only be achieved by either moving the sound source away from the recording horn, or by gradually reducing the volume at which the performer were singing, playing or speaking. With the advent of electrical recording, smooth and controllable fadeout effects could be easily achieved by simply reducing the input volume from the microphones using the fader on the mixing desk. The first experimental study on the effect of a fade-out showed that a version of a musical piece with fade-out in comparison to the same piece with a cold end prolonged the perceived duration by 2.4 seconds. This is called the "Pulse Continuity Phenomenon" and was measured by a tapping-along task to measure participants’ perception of pulsation.
An 1894 78 rpm record called "The Spirit of '76" features a narrated musical vignette with martial fife-and-drum that gets louder as it nears the listener, and quieter as it moves away. There are early examples that appear to bear no obvious relationship to movement. One is "Barkin' Dog" by the Ted Lewis Jazz Band. Another contender is "America", a patriotic piece by the chorus of evangelist Billy Sunday. By the early 1930s, longer songs were being put on both sides of records, with the piece fading out at the end of side one and fading back in at the beginning of side two. Records at the time held only about two to five minutes of music per side. The segue allowed for longer songs, symphonies and live concert recordings.
However, shorter songs continued to use the fade-out for unclear reasons—for example, Fred Astaire's movie theme "Flying Down to Rio". Even using fade-out as a segue device does not seem obvious, though we certainly take it for granted today. It is possible that movies were an influence here. Fade-ins and fade-outs are often used as cinematic devices that begin and end scenes; film language that developed at the same time as these early recordings. The term fade-out itself is of cinematic origin, appearing in print around 1918. And jazz, a favorite of early records, was a popular subject of early movies too. The same could be said for radio productions. Within a single programme of a radio production, many different types of fade can be applied. When mixing from speech to music, there are a few ways that fade can be used. Here are three examples.
- Straight: the introduction has become a musical link between the music/speech that follows, additionally the first notes of the intro can be emphasized to make it pop out more.
- Cutting the introduction: Since the first word of the vocals has to follow promptly after the cue light, it could be used to move the recording onward.
- Introduction under speech: The music is placed at the specified time on the cue, the level must be low in order for the vocals to be audible. Here the fade-up generally occurs just before the final words in order for the cue to be given. In stage productions the closing music is played from a predetermined time and fades up at the closing words in order to fit in exactly with the remaining program time.
Contemporary
No modern recording can be reliably identified as "the first" to use the technique. In 2003, on the website Stupid Question, John Ruch listed the following recordings as possible contenders:More recently: "At the meta-song level, the prevalence of pre-taped sequences emphasizes the importance of flow. The effect on radio pop programme form a stress on continuity achieved through the use of fades, voice-over links, twin-turntable mixing and connecting jingles."
Fade
A fade can be constructed so that the motion of the control from its start to end points affects the level of the signal in a different manner at different points in its travel. If there are no overlapping regions on the same track, regular fade should be used. A smooth fade is one that changes according to the logarithmic scale, as faders are logarithmic over much of their working range of 30-40 dB. If the engineer requires one region to gradually fade into another on the same track, a crossfade would be more suitable. If however the two regions are on different tracks, fade-ins and fade-outs will be applied. A fade-out can be accomplished without letting the sound's distance increase, however this is also something it can do. The perceived distance increase can be attributed to a diminishing level of timbral detail, not the result of a decreasing dynamic level. A listener's interest can be withdrawn from a sound that is faded at the lower end since the ear accepts a more prompt rounding off. The fade-in can be used as a device that separates the listener from the scene. An example of a mini fade out, of about a second or two, is a sustained bass note left to die down.Shapes
The shape of a regular fade and a crossfade can be shaped by an audio engineer. Shape implies that you can change the rate at which the level change occurs over the length of the fade. Different types of preset fades shapes include [|linear], logarithmic, exponential and S-curve.Linear
The simplest of fade curves is the linear curve and it is normally the default fade. It takes a straight line and introduces a curve. This curve represents an equal degree by which the gain increases or decreases during the length of the fade. A linear fade-in curve makes it sound as though the volume increases sharply at the beginning, and more gradually towards the end. The same principle applies on a fade-out where a gradual drop in volume can be perceived in the beginning, and the fade gets more abrupt towards the end. Because of the initial drop in perceived volume, the linear shape is ideal if there is a natural ambience or reverb present in the audio. When applied it shortens the ambience. Also if the music requires an accelerating effect, this linear curve can also be applied. This type of fade is not very natural sounding. The principle of a linear crossfade is: at the beginning of the fade the perceived volume drops more quickly, one can see at the halfway point that the perceived volume drops below 50%. This is a very noticeable drop in volume. Also if the control can move from position 0 to 100, and the percentage of the signal that is allowed to pass equals the position of the control. At the midpoint of the fade the effect of a linear crossfade is that both the sounds are below half of their maximum perceived volume; and as a result the sum of the two fades will be below the maximum level of either. This is not applicable when the two sounds are on different levels and the crossfade time is long enough. In turn if the crossfade is short the dip of the volume in the middle of the crossfade can be quite noticeable.The level of the signal as a function of time,, after applying a linear fade-in can be modeled as follows:
where:
- is the original level of the signal,
- is any time in the fade,
- is the start time of the fade,
- is the end time of the fade.