A non acoustically treated room can sound very messy and be hard to listen to. If you've just noticed room problems though and already made a couple of episodes. Or If you made an interview at another not so ideal location, there are fortunately ways to partly deal with room sound. As a podcast editor I face these problems all the time and most of the time re-recording is not an option. That's why I use this method to reduce room sound in my podcast and you can too. You will probably not get it as good as making the adjustments prior to recording, but it can most definitely make a difference!
Before we begin taking a look at the tools we need to talk a bit about sound relative to time. Every sound has a beginning and an end. In sound terms these are usually described with the words transient and sustain. A sound can have very fast transients, like drums and percussion, or slow transients, like violins or organs. If a sound very shortly dies after the transient it has short sustain. If it continues for a long time it has long sustain. The same examples applies here since drums mostly have short sustain and violins have long sustain. At least if they are used in their most conventional approach!
Something that does indeed alter the transients and the sustain of instruments are rooms or different locations. A drum kit played in a big cathedral or church will have a lot more sustain than if played in a wardrobe. Just take a listen to this Led Zeppelin song if you don't believe me.
But how does all this music lingo apply to podcasts then? Well, spoken word is no different in this regard and if you record in a non treated room your voice will have a longer sustain. So with this information we can start looking for the tools to help us reduce the sustain of our recording.
There are actually a lot of such tools out there and many of them are free (I'll include a short list at the bottom). Some come with the audio software of your choice as well often named something in the fashion of Transient Shaper, Transient Designer or Envelope Shaper. These are usually pretty simple tools with two or three knobs named transient/attack and sustain. Begin with grabbing the sustain knob and reduce it to hear some of that room echo disappear!
Here are a couple of free tools for reducing sustain: