Fades

Peter 14Nov12: created this page.

• Once Steve's Wiki page on fading is published I would anticipate that we would link to it from this page.
• Gale: 14Nov12: It's a bit bare bones, and mostly duplication of the Effects page (apart from the images). Is there any more we can say? Something about what fades may be useful for? If/when we get Adjustable Fade shipped, would it go here? I am not sure it would. Perhaps this page should be for "automatic" fades?
  • How about an image of Cross Fade after mixing, to show what we mean by equal volume after the mix?
  • I can't see the point repeating the tips box both here and on the Effects page. I would suggest only having it here, if we want this page.
• Peter 15Nov12: Yes it is a little bare bones, but I was deeply conscious that this is the Manual and that thus here we need basically state what the commands do rather than how to effectively use them (in line with the documentation of the other effects). Use of the fade commands is complex tutorial material and I was intending to point this page at Steve's nascent tutorial on Steve's use of fades tutorial (which is currently under development in the Wiki but could IMO earn a useful place as a tutorial in the manual).
  • Personally I find it useful to see the images of the various fades together on this page for easy visual comparison and I would hope that other readers would find that similarly useful. I was careful to keep the images and fades visually constant to facilitate such comparison.
  • I have added an "After Cross Fade" image as you suggested - though I'm not entirely convinced of its utility here (see comments above re tutorial material).
  • I agree that it's not worth repeating the note box on Effect Menu and here, so I have commented it out there for now. The note box here has slightly more information than the Effect Menu one - one extra bullet point.
• Bill 05Jan13:
  • It seems we've reversed the normal usage of note and intro templates on this page. The page starts with a note at the top, then uses intros after each major heading. Regardless of the colour of the box, surely "tips" should not be at the head of the page? Tips ("semi-tutorial" material) have usually gone at the end of a page or section.
  • If we feel this page needs an intro, would it make sense to introduce the fact the Audacity ships with several "types" or "flavours" of fade effects?
  • In this case I am minded to agree with Ed, and would prefer the introductory paragraphs to be plain text.
• Peter 6Jan13: Good catch Bill - and sorry that was my fault. There never was an intro note to this page (an ommission I have now corrected) and when I moved the tutorial-type note from the bottom to the top that's wat caused a "note" to be topmost (Connie would not be pleased with me). I also plain-texted the stuff below the headers.
• Gale 11Jan13: I've now read this and tweaked the text (generalising fade direction so it applies to both fade in and out) and moving fade ins above fade outs as they appear in the app.
  • I removed the H1's which are incorrect for screen readers (the page title is the only H1 - see Consistency). If you want HR's for each effect (I think they add nothing) please add them.
  • I added a P1 for incorrect "after cross fade" image. Clearly when to use equal power and when equal gain fades should be discussed somewhere. I'm OK with a replacement image for "after cross fade" and then an image in the Adjustable Fade section to show an equal gain curve. Otherwise, Adjustable Fade has no corresponding tone image like all the other fades here, which looks a bit odd.
    • Peter 11Jan13: Surely Steve's as-yet-unpublished Wiki page on fading is the correct place to have such tutorial material? Or maybe Steve's fade page should be published as a tutorial in the manual? But not for 2.0.3!
    • Peter 11Jan13: It seemed somewhat pointless to provide a tone image (similar to the other fades) for adjustable fade. The whole point of AF is that it is "adjustable" and can be used to produce a plethora of different customizable fade shapes, not just a single one. Accordingly I thought it more appropriate to show an image of the dialog box here with the controls that are available. I realize that this provides duplication with the Adjustable Fade page, but I think it is worthwhile as it will show the reader of this page the potential scope and power of AF and encourage click-through exploration/
    • Gale 11Jan13: ToDo-2 I think the reservation about "no tone image" is valid irrespective of the P1 for incorrect "after cross fade" image. I would like (at least to consider) a "simple" image of a partial fade without the added complications of mid-fade boost in the image on Adjustable Fade. But only a P2 and no need to do for 2.0.3.
      • Peter 12Jan13: I added in the tone image that Steve created for the Adjustable Fade page. Yes it is repetitious but I think it bears repetition by being on this page too; I like the fact that it shows more than one fade created with AF.

Audacity ships with several types of fade effects: a pair of simple linear fades, a pair of fades to help you make a crossfade, a more musically pleasing fade out (similar to that used in many recording and mastering studios) and a powerful customizable fade.

Linear Fades

These basic fades apply a fade to the selected audio such that the amplitude of the selection goes from absolute silence to the original amplitude (Fade In), or from the original amplitude to absolute silence (Fade Out). The shape of the fade is linear, so it appears as a straight line from beginning to end (when viewed in the default linear Waveform View Mode). The speed of the fade in or out is therefore constant throughout its length and depends entirely on the length selected for the fade.

Fade In

Accessed by: Effect > Fade In

Gale: Then why not an image of a fade in with a shorter selection than fade out? It lets people see the difference the selection length makes.

• Peter 17Nov12: I thought long and hard about this before I constructed the images. I finally decided that the most important thing on this page was to document the effects themselves rather than their usage (that to me is tutorial material as in Steve's emerging Steve's use of fades a referenced above) - accordingly I wanted the users to be able to directly visually compare the fade shapes. Note too that there is actually no timeline/timebase in the images,so the fade length is not specified directly in the image.
  • Gale: Not a big deal, but I am not entirely convinced. "Unlike fading out a fade in is normally applied over a very short audio selection (less than a second)" is surely itself "tutorial material" (and is "less than a second" correct?). I agree it's good to let users compare like with like, but if you choose to introduce the comment about what the fade in is used for, it's confusing to then have the selections the same apparent length, timeline or not. Maybe have an additional image to show the difference the length of selection makes?
    • Peter 11Jan13: I tried creating an image with short fade-in at normal zoom and I found that it makes it too hard to really see the fade's shape. The advice on fade lengths comes from earlier discussions with Steve when I have been testing fades for him - and I believe his advice comes from his practical experience on mixing desks. I've tried longer fade-ins in the past and to me they seldom sound right. Often I'm shortening an intro when a DJ is talking over the beginnining of the track and what I want to do is pick up on a following beat and produce a short fade-in (using 3xlinear fade on advice from Steve). The "tutorial" information here on 3xfade can disappear if and when in the future we get a Studio Fade In to complement SFO.)
• Gale 11Jan13: OK I accept your arguments on this.

A fade in is often applied over a very short audio selection (less than a second). You may get a more "musical" result by applying a linear fade in three times to the same audio selection. This approximates an exponentially shaped fade in.

Fade Out

Accessed by: Effect > Fade Out

A fade out is often applied to a longer selection than a fade in, typically to a selection up to about ten seconds long.

Cross Fades

Despite their names these effects do not perform an automatic "crossfade" between two tracks or adjoining audio, where the audio coming to an end would fade out at the same time the following audio fades in. Instead Cross Fades apply a curve that is different from the linear Fade in and Fade Out. The curve used is one that will result in equal RMS (average) volume throughout the faded section once the faded in and faded out sections are mixed.

As with linear fades and Studio Fade Out, the fades are between silence and original volume.

Cross Fade In

Accessed by: Effect > Cross Fade In

Cross Fade Out

Accessed by: Effect > Cross Fade Out

Gale 11Jan13: ToDo-1 You may get your wish not to have an image of "after" because the image below is obviously incorrect. Since two tones are phase-coherent, the result will be a bulge of peak amplitude (though rms will be constant). It might actually be useful to show this with the recommendation to use an "equal gain" curve (S-Curve in Adjustable Fade?) for phase-coherent material. There would be an equivalent image in the Adjustable Fade section to show the peak level constant but the rms falling away mid fade.

• Peter 11Jan13: The proper "after" image looks distictly weird with the bulge - it will look wrong to many users. Even Steve's "Cross Fade Classic" plug-in produces a power bulge, but that is biased towards the beginning of the crossfade rather than centred as with Cross Fade In/Out. I would vote strongly for removing this image altogether.
• Gale 11Jan13: Yes the "proper" image does look weird and would have to show a lower amplitude tone. It can't stop as it is, so I think this is probably out, but I do think some text could remain about "after cross fade". The current almost complete lack of help with crossfading is a significant blemish in the Manual IMO. I'm going to sleep on it, I suggest you do too.
• Bill 11Jan13: Even with noise you get the bulge, but not with music. Music may not show the shape as well, but does show the "equal volume" better.
  There's a problem with the existing 'before' images - the Cross Fade effects create clips when applied and this is not shown in the images.
  Would these images be better?
• Gale 11Jan13: Thanks, Bill. Good catch, the Cross Fade "before" images must have split lines. I think quite strongly that the the "before" images should be tones in order to clarify the shape. The upper track in your before image could easily look linear to an inexperienced eye.

  We could show only the "after" music image to demonstrate that volume "looks equal" throughout the processed fade. Or we could reduce the height a little of the two "before" music images (or reduce height of the "after" music image as well). ATM I would tend to favour just showing the "after" music image, enhanced with arrows to show where the fade was, since render removes selectedness of the mixed track. Probably we should make that enhancement even if we show all three music images.

• Peter 12Jan12: This just shows the conundrum here. Like Bill I began experimenting with fades on real music as neither tones nor noises gave a "sensible looking" after image. And I agree with Gale that the musical examples normally fail to properly show the fade shape. This is why I cheated with a faux-image in the first place :=)) Personally I still don't think we need to bother with an after-crossfade image on this page - it will be better dealt with in Steve's developing fades page - which increasingly, I think, should become a tutorial in this Manual and not the Wiki where it is now. For now it would leave a slight gap in the manual on the usage of crossfades - but that gap exists now in the current manual and the one for 2.0.0. I would just like to see it as a priority for us in the editorial team to help Steve get his work on the fades tutorial polished and ready for publication in the 2.0.4 Manual that we will start on soon.
• Bill 12Jan13: New images using heavily compressed music. I think these show the "bullet nose" shape adequately. After image has fade region selected for clarity.
  On further reflection I think the current after image is likely to cause confusion even though it is technically correct. We say the RMS level is contant, but a reader who looks at the image and doesn't read the text (or doesn't click through to the definition of RMS) is going to question our assertion that these effects, when mixed, produce an "equal volume" cross-fade. However if we go back to the "faked" image, the technically minded are sure to call us out on it. So, my preference is either to have no 'after' image, or use music for the three images.
• Steve 12Jan13: The original "faked" image was just wrong and stood out like a sore thumb. I like Bill's new image (below) but it does not show that peak levels will often be higher than the pre-mixed tracks (which is clearly shown with white noise. I like the white noise image a lot because it shows an increased peak level and the assertion that the "loudness" is constant. I think that the apparent contradiction is one of the clearest demonstrations that "loudness" relates more closely to rms level than to peak level. Could we include both a cross-faded white noise and a cross-faded music example? Can images be captioned?

After a Cross Fade

If the two waveforms above (Cross Fade In and Out) were on separate tracks then rendered so as to mix the waveforms together, an equal volume section of audio would result as below. The example uses constant amplitude white noise to illustrate the fades and shows that the rms level (the pale blue middle part of the waveform) remains at a constant level - normal audio would appear more spiky, though still having the same average volume.

Crossfading by hand should be performed by overlapping the parts to be faded using two separate tracks. A general rule that avoids a loss of perceived volume mid-fade is to use the two Cross Fade effects, or the "Cosine" presets in the Adjustable Fade effect.

• Depending on the material, both these methods might cause a gain in peak amplitude with a risk of clipping. In that case, try using the linear fades or the "S" curves in Adjustable Fade.

Gale 01Jan13: Probably we should not have a "Musical Fades" (plural) section until we have Pro Fade Out released on Wiki (or in 2.0.x)

• Peter 1Jan13: I added a temporary header "Additional Shaped Fades" until we can un-leash "Musical Fades". SFO and AF are not part of "Crossfades" so need their own umbrella header.

Musical Fades

These fades apply a more "musical" fade to the selected audio, giving a more pleasing sounding result.

Additional Shaped Fades

Studio Fade Out

Accessed by: Effect > Studio Fade Out

Gale 01Jan13: This is confusing. Which of the mirrored S or 1/2 period curves does it use, when? Or are they the same thing?

• Peter 1Jan13: I changed the description to that on the Effect Menu page. Previous text was "Produces a smooth and musical sounding fade out. A mirrored S-curve or 1/2 period cosine is used for the volume and a linear ramp for the low pass filter (from 22050 Hz down to 100 Hz)."
• Gale 02Jan13: It's up to Steve if he wants to explain about the curves, but I think it is un-necessary detail on this page. Removed "professional" in favour of "studio". "Professional" is too contentious, as Vaughan says.
  • Peter 4Jan13: I softened the description by moving the techy details into a tech-note rather than having them up-front first in the desciption - this should enable us to demote the P1 to >P2.
  • Peter 6Jan13: I moved the technote into an ednote to comment it out - and accordingly removed the P1 from here.

Produces a smooth and "musical" sounding fade out from original volume to silence by applying a doubly-curved (S-shape) fade and fading out the higher frequencies a little quicker than the lower frequencies. It gives a "going off into the distance" type of sound rather than sounding like a "mechanical" fade out. This technique has found favor in recording studios for CD and LP tracks.

Peter 6Jan13: I decided to comment-out this technote, at least for now. I don't see what it adds over the simpler textual description provided (except for the experts in digital signal processing). This enables us not just to be able to demote the above P1 but remove it.

• Gale 11Jan13: Nonetheless there is some confusion invited now as it may appear that retaining the bass is giving this distinctive "S" shape however AFAIK the filter is not shaping the curve that much, the shape comes mainly from the choice of shape. But you should ask Steve.
  • Peter 11Jan13: I have added some text about the fade shape - my understanding from earlier long discussions with Steve is that this fade achieves its musically pleasing nature fro a combination of the S-shaped (sinusoidal) curve together with the use of the progressive filtering. But I think that we probably don't need that level of detail - we do beed to encourage users to try it however and I feel that too much techy detail may put them off.
  • Gale 11Jan13: I'm happy with your text. AFAICT the essential "S" shape persists even with a very high or very low frequency tone. There is now no implication the filter is creating the "S" which was my concern.
  • Steve 12Jan13: For clarification, Gale is correct. The filtering can affect the shape a little, but only a little. The shape is essentially sinusoidal and comes from the "fade" rather than the "filter".

Technical note: this effect works by applying a sinusoidal fade with a progressive low pass filter from full spectrum at the start of the selection to 100 Hz at the end.

You can make a simple customization of the shape of any of the above fades by repeating it using Repeat Last Effect ( CTRL + R ). If you repeat a fade in, the audio will remain quiet for longer then rise more rapidly to the original level. Repeating a fade out will cause the level to initially drop more rapidly then tail off at a lower level.

Peter 12Jan13: Looking at this page as a "civilian user" I would prefer us to move the content of this note into the intro div as it seems to get somewhat lost down here.

Gale 01Jan13: ToDo Pro Fade Out has been committed for 2.0.3 as "Studio Fade Out", but as yet we have no Studio Fade In ready to release.

Studio Fade In

Accessed by: Effect > Studio Fade In provided you have installed it.

Adjustable Fade

This has a dialog box where you can choose the shape of the fade in or fade out to be applied. You can also create "partial" fades to and from other than silence and original volume. An example of this might be a fade in from 20% of the original volume to 80% of the original volume. The "Handy Presets" at the bottom offer a choice of six pairs of fade in or fade out shapes, fading between silence and original volume.

Accessed by: Effect > Adjustable Fade...

Choosing a preset disables all the other controls irrespective of their setting. Therefore to make a partial fade you must choose the Start and End values then use the other controls above to determine the fade shape and direction.

Examples of fades that can be achieved with Adjustable Fade

ToDo Gale 01Jan13: Adjustable Fade has been committed for 2.0.3. Review if this should go at the bottom of this page and the text here.

• Gale 11Jan13: I'm not sure all of these tips below are in the correct place here. I removed the last tip about longer fade outs which was duplication.
  • Peter 11Jan13: I'm not sure now that I like any of these tips, not just here but anywhere on this page. For a start is the Envelope Tool advice still vaid now that we have Adjustable Fade? I've always been iffy about the so-called 2/3 rule in point 3 in the note - I seem to remeber some (largely unresolved) debate about this in the past; so is it valid, do we need it?
  • Gale 11Jan13: Re the "repeating" tip, I think it remains useful as a less scary (and quick) alternative to Adjustable Fade. I've tried moving it up so it's under Studio Fade Out.

    Yes, we must mention Envelope Tool I think. Some people will prefer the visual GUI and others will want multiple envelope points. I tweaked the note, leaving it where it is for now.

    The objection to the "two-thirds" rule is that it may increase peak amplitude even for linear fades. But since I hear more complaints about "mid-fade drop" than clipping, I think we want this hint at least until we actually have Steve's definitive Cross Fade Wiki page (and even then it provides somewhere to give the link). I moved this note underneath Cross Fades. I think these three changes are something of an improvement.

  • Steve 12Jan13: I have removed the tip about the "two-thirds" rule as that "rule" exists as a rough approximation to an "equal power fade" (from when Audacity did not have such a thing). As Audacity now has multiple ways to produce "equal power fades" (the "Cross Fade In / Out" and "Rounded" or "Cosine" presets in "Adjustable Fade", we don't need to resort to the 2/3 rule.

Envelope Tool on Tools Toolbar enables you to make completely customizable exponential fades having unlimited points along the fade, using a volume envelope in a separate track.

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