Audio Loops are valuable tools for a sound designer. When edited correctly, audio loops can be seamless and infinitely repeatable. Looping can save valuable editing time, and can preserve the fidelity of your audio without hogging large amounts of storage or computer processing power.
What is an Audio Loop?
An audio loop is a repeating section of sound material, in which the audio file (or region) begins and ends with the same exact audio information. If two instances of the file are played back-to-back, they will sound seamless. Loops are most commonly viewed as a tool for producing electronic music, notably in programs like FL Studio, Garage Band, or Sony Acid. They are cut to sync to a beat or rhythm, thus the loop can be repeated over and over again to produce a song. These loops are generally only a few seconds long.
Audio loops created for the purpose of sound design are generally arrhythmic and are longer than a few seconds. I recommend a minimum 20 – 30 seconds for ambiences to avoid distinct sounds within the ambience from being noticeably repeated.
How to Create a Seamless Loop From an Audio File
Let’s use a simple wind ambience as an example. For the purposes of this tutorial, you can view and download this wind ambience file HERE. Work along with the tutorial in your preferred DAW (Digital Audio Workstation). I will be working in Pro Tools, but you can do this with just about any editing program. If you don’t have one, you can download Audacity for free HERE.
STEP 1: Create Your Loop Point
Pick an area approximately 1/4 of the way from the end of the audio region. Separate the region into two parts at that point. In Pro Tools, while on the selection tool, use the key command [ COMMAND ] + [ E ] on a Mac. This break will become the starting and ending point of the finished audio file that guarantees seamless transition.
STEP 2: Flip Flop the Audio Regions
Drag the first audio region—that is the one on the left—across so that is on the right side of the second audio region. You may want to trim off the very beginning of the audio as it usually has a pre-built fade in. Then drag region 1 part way over region 2. Look for a point in the waveform where the transition between audio region 1 and region 2 have similar amplitude and tonal quality.
STEP 3: Cross-fade & Consolidate
Cross-fade the boundary between audio region 1 and 2. You may need to adjust the length and curve of the cross-fade to find a transition that is unperceivable. Next, select everything (regions 1 and 2) and consolidate them into one new audio file. In Pro Tools, you can do this by pressing [ SHIFT ] + [ OPTION ] + [ 3 ] on a Mac.
The finished result is a new audio file that can be seamlessly looped. Test it out by doing a copy/paste with the audio file back to back in your DAW.
Benefits of Creating Audio Loops
Let’s recap in detail the benefits of creating loops for a variety of audio applications:
In post-production film, where we work in a DAW, you can copy and paste your loop as many times as you need in an ambience track instead of having to re-create a cross-fade every time. This saves valuable editing time.
In video game applications where the allotted memory for sound effects is minimal, creating a small seamless loop in conjunction with programming will save disk space and ensure a continuous ambience during game play.
In live theatre applications, where the timing of a moment on stage is not consistent from show to show, audio loops can be used in conjunction with show control programming to ensure the sound design stays in sync with the action. For example, I designed the 2013 Inge Festival’s production of Bus Stop in which the soundscape called for a continuous snowstorm and a bus to arrive outside. I created two ambience loops; one for the “interior” wind howl and one “exterior” wind that could be faded in and out as characters opened the front door of the diner. When the "bus" arrived (an offstage sound cue), the engine was supposed to idle in the background until a specific action on stage cued it to turn off. In order to accommodate the inconsistent time span associated with this live performance, once the bus arrived, I cross-faded the sound cue into an idle motor loop. The motor loop could then be triggered to cross-fade into a “bus power down” sound cue at the specific cue moment.
Creating loops, as well as knowing when it is best to use them, can be a powerful and worthwhile tool for a sound designer. Get clever with your programming and design with audio loops in mind. You may be amazed how efficient and truly diverse their uses can be.