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Not Designed for this Part 2: Sound Design with Feedback Noise

At its core, every DAW (Digital Audio Workstation like Ableton Live or Logic) is a simple input / output system: Sound goes in, is processed and then output. With that in mind, let’s think about how a simple feedback loop can be used to generate some unexpected sounds.


WARNING!

Before you do this, make sure you keep your volume low and watch your meters, so you don’t damage your hearing or your speakers. Please follow the instructions below regarding volume levels. We cannot be responsible for damaged speakers or hearing.


Setup

This requires a little bit of setup and tinkering with system settings. For this i’m using a simple USB audio interface so i can route sound out of the interface and back into my laptop while still having access to another output to monitor my results.

In order to achieve this we’ll need to set up an Aggregate Audio Device, where for the input the USB interface acts as Channel 1 & 2 and for the output the USB interface acts as Channel 1 & 2 out and the headphone output acts as Channel 3 & 4 out. (Your setup may be different, but in my case i’m using my laptop which only has a single 1/8″ stereo output)

Setting up an aggregate audio device on a Mac (Tutorial by Apple) »

Setting up an aggregate audio device on Windows (SoundOnSound. This is the best tutorial i could find, but if you have anything better, please post it in the comments) »

You’re also going to need to run a cable from your computer’s audio output into your audio interface and either headphones, or another cable to go from the output of your interface to your headphones / mixer & speakers. Here is my setup:

DAW Setup & Routing

Hopefully the setup part wasn’t too complicated and you can now move on to routing your audio into a feedback loop inside your DAW. For my example i’ll be using Ableton Live.

Open a new project and then open your preferences. Set your audio input and output to your aggregate audio device and make sure that Channel 1&2 are set as the input and Channels 1 thru 4 are set as the output:

Close the preferences and create 3 Audio Channels. Make sure to set each channel to -60dB! At this time, i want you turn your mixer’s volume all the way down – just to be safe

Channel 1 is your Feedback loop, which takes the audio output from your computer and receives it on the USB Interface’s input. Channel 2 is necessary to hear the signal and takes the audio from Channel 1 and sends it to your monitoring source (Headphones / Mixer). This is also where you’ll be running your effects plugins to turn the harsh feedback signal into something cool. The 3rd channel takes the audio from Channel 2 so you can record the results.

My Channel 1 is labeled “Audio 2” here and my Channel 2 is labeled “Effects”

Because the feedback signal is continuous, there’s no way to stop it when you press Stop in your DAW. So let’s put a Utility at the end of our FX chain (i put mine before the Reverb) so i can mute the signal and still get a nice reverb tail.

Ok, time to make sound: While keeping all other channels at -60dB, turn the audio for Channel 1 up to 0dB. You’ll see the levels go up pretty quickly, and may start to hear some noise. Now, VERY SLOWLY turn up the volume for Channel 2. You’ll immediately hear a horrific noise that sounds a bit like the Hypnotoad:

For the purpose of this example, i’ve added the following effects to my Channel 2: Resonators, Corpus, Chorus, Auto Filter with LFO, Utility (my kill switch) and Reverb. You can add any effects you like, but i recommend you add 1 effect at a time, KEEP THE VOLUME LOW and monitor the results. Here’s what i’ve come up with using the rather irritating feedback signal:

Of course there’s still more work that could be done to this sound like better EQ settings, perhaps a really high-end reverb like Eventide’s Blackhole, or maybe something to mangle the sound even further like a granular delay…ok, i could go on…

Let’s take this 1 step further and intercept our feedback signal with a little outboard effect. For this i’m going to use my Monotron Delay, which may be a cheap toy, but is actually a very powerful analogue synth and filter. I’m going to run my computer out signal into the Monotron and then go from the Monotron again into my USB Interface input. Now i can use the Monotron’s analogue filter, lfo and delay to change my feedback signal before it’s processed by my effects in Live. Here’s what that sounds like:

As you can hear it creates a pretty interesting and dramatic sound. Almost reminiscent of something i’d expect to hear in a dark SciFi movie. Hopefully you’ve found this little journey into the weird world of sound useful and maybe i’ll do a Part 3 using only hardware.

Stefan Weise has over 20 years of music production and DJ experience, and is the host of the monthly Blue Industries show on Proton Radio. He also operates his own label 3km Records and is an occasional contributor for Audiophile News.

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