Using Expanders in audio

 
I was talking with a very good friend of mine, recently, about posting topics for the Home Recording Weekly blog. I expressed that I have been tossing around the idea of writing a "series of posts" covering some of the basic tools of our trade. He liked the idea, and he agreed with the idea, and then added to it by saying "Content is king". Simply put, and yet right on the mark. Content is king indeed. Not only have I decided to write this series of posts, but I have decided to start with a tool known as the expander.

Expanders..... What are they, and how do we use them in our audio? These are some great questions, and I really hadn't used one before too long ago. Recently, I was using a different "audio tool" in place of an expander, and the results were less than stellar. Since then I have fallen in love with Expanders, and need to share what I have learned.

Let me detail what it is that expanders do, and then I will tell you what I was using in its' place.

Expanders are a tool that we can use in out tracks to help clean up audio. Expanders can be set, much like a compressor, to "work" or "turn on" once a threshold has been crossed. Compressors do not operate until a threshold has been crossed, and once they turn on they reduce the output or reduce the signals output. However, unlike a compressor, once the desired threshold is crossed in an expander, the expander then acts more like a switch. Once the threshold is crossed, the expander "opens" and allows audio to pass through untouched.

You might be thinking about noise gates right about now, and asking yourself why I didn't use a noise gate as a comparison in this post, you know, instead of a compressor. Expanders can be thought of as a noise gate, but they do operate differently than noise gates. There are some important features that expanders have that most noise gates do not have. For example, expanders will not only allow a threshold to be set, but you can adjust the range, attack, release, and most importantly, "the hold".
Most of the noise gates that I have used in the past, are either "on or off", or "allowing audio to pass or not allowing a signal to pass". There are no settings like "the hold" feature found on an expander.

 So, what is "the hold" feature? The hold feature tells the expander how slowly, or how quickly, to toss the switch once the threshold is released, or shut off. This can act like a simple fade, so that the switching on and off does not stand out. The "hard" clicking on and off of audio can be noticed. That is the reason noise gates can often times be "heard" when used, and expanders can not be "heard" or audible. That is why I decided to use compressors as a reference, and not a noise gate.

Let me explain how I have been using an expander lately, and why a noise gate would not work in this particular case.

I have been mixing a rather popular, and new podcast. This has proven to be a blast, and I look forward to each new episode that I am handed. As usual, I had some interviews that needed to be mixed in with the podcast. The interviews are actual conversations via Skype, with each person using headsets, and recorded using Audacity. These interviews come to me on two mono tracks, with one speaker on each track. So, as one speaker stops talking, the other speaker starts talking. In between the talking there is a lot of noise, like interference and electronic jittering. I almost started to remove this noisy, dead space in between the speaking parts by simply deleting it, and then use fades to bring the speaking parts in and out. This would have taken a very long time, and been rather tedious. So, I decided to "drop" an expander on each of the two mono tracks, and see just how well I could do at removing this noise. You will need to watch the video to see how I set it up, but let me just say that it worked like a charm.



The important thing that I hope you retain, here, is that I saved myself a lot of time and frustration by using an expander. Since this mixing gig is a paying job, the less time I spend editing, the more money I make. Well, when figured out using the "paid by the hour" formula anyway. Truth be told, I make a set fee with each episode that I mix. So, in this case, time really is money. Plus, I avoided a major headache by not having to delete a ton of track, and then add fades all over the place. Yet another thing thing that I want you to remember here is that a noise gate (most likely) would not have worked as well, if at all, in this particular situation. Why not? Great question. Let me answer that one.


Without the "hold" feature found on expanders, the "switch" that allows audio to pass through would either be "on, or off". This hard switching on and off is not only audible to the listener, it can become very annoying! Most people would not want to listen to the interview, let alone the podcast, and that would be bad news for me! A noise gate has its' place in audio, and can be wonderful for a lot of things, but an expander is just way better for this particular application.

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