Podcast Audio Editing using Audacity

Editing Podcast Audio Using Audacity

Scope of this guide: Using the free audio editing software, Audacity, to edit recorded podcast audio.

• Downloading Audacity and its .mp3 plugin.
• Loading recorded audio for sound improvement:
  • Raising or lowering the gain (audio) to YouTube/CD levels.
  • Using filters and noise reduction to improve audio listenability.
  • How to time-shift selected audio.
  • Adding effects like fade-ins, fade-outs and auto-ducking music.
  • Exporting the final edit as an .mp3 or .wav soundfile.

If you haven’t already, download and install Audacity. 

Make sure to download the LAME .mp3 plugin. I recommend Sourceforge.

Audacity work space:

1. Open Audacity.
2. File>Open>select recorded audio file to edit from folder on your computer.
3. It will “paint” the waveform, in blue, along the timeline.

Tour of Audacity’s features

• Pull down menus we will be using: File, Edit, Tracks, Effect.
• Icons above the waveform to note, left to right:
  • Selection tool (looks like an I with bar on top and bottom).
  • Spyglass + (Zoom in); Spyglass – (Zoom out).
  • Next to the speaker icon, (center), is the sound meter which displays the sound on playback; measured in decibels.

Filter effects

When I edit a podcast, the first thing I do is run several filters; in sequence.

Under the pull down menu for Effect, select in this order, filter one at a time:

• Compressor – Reduces the dynamic range of a recording which will increase the gain (jargon term for volume) to an ideal level throughout the recording.
• Normalize – Sets the peak amplitude to a range that avoids clipping (jargon term for a volume peak that is too loud for the file). It also equalizes the waveform between left and right channels.

• Limiter - Caps the gain at a certain decibel level to prevent clipping while not affecting any of the audio below the set limit.

• Noise Reduction – It is good practice when recording audio to allow a 10-20 second segment of silence. Every room, even soundproofed rooms, have a room tone.

Capturing that “noise” will remove that tone throughout the entire file. You do this so that gaps between audio don’t resonate as much on the sound meter/audible playback.

In order to filter a sound file, the audio must be selected:

1. Place your cursor, anywhere on the waveform, using your index finger on the left edge of the mouse.
2. Command-A (Mac) or Control-A (PC) selects the audio which turns the waveform from grey to white.
3. Pull down Effect menu, choose in the above order (Compressor, Normalize, Noise Reduction).
4. Leave default settings as is, for each filter, and click OK.

• For noise reduction, do not select all audio. You want to select your room tone portion by placing your cursor at the beginning of the silence and “wipe right” by holding down on the left edge index finger motion and drag right.

 

1. Return to Noise Reduction under Effect.
2. Click Step 1 “Get Noise Reduction”.
3. Return to the waveform and now select all the audio being noise reduced.
4. Effect>Repeat noise reduction which will comb through the entire soundfile and remove mostly “hum” and “rumble” or other sources of noise pollution.
5. It does not work miracles, however. Over using Noise Reduction can make your edit sound “dry” or “brittle”.

Caveat on non-destructive sound editing: Any effect or edit you make, can be “un-made” without destroying the original recording. To undo any action:

• Pull down menu>Edit>Undo whatever effect or edit you made.

Ideal audio rule of thumb: YouTube audio ranges between conversational levels of -18 db (decibels) to -12 db. Peaks should not be louder than around -4 db.

• Place your cursor randomly along the waveform.
• Spacebar engages/stops playback.
• Look at the meter reading. It should be mostly in green while “bumping” up against the yellow.
• If you hit red, your file is too loud. A red clip mark will fix itself as proof you need to lower the gain to the ideal: green to yellow blend.
• Clipping over amplifies the speaker source which has a crunching, annoying sound on playback.

Adjusting the gain (volume):

• Select the audio or portion of audio you want to re-amplify:
  • Select and "wipe" the audio.
  • Command-A/Control-A for the entire clip.
  • Selected audio shifts to white from grey.
  • Pull down menu>Amplify>slide left, into minus db range, to decrease the gain; slide right to increase the gain.

Robert’s rule of thumb: “between the fives”.                                                              .

On the far left of the waveform, before the audio file, are the volume parameters for your soundfile: 1.0, .5, 0.0, -.5, -1.0.

I edit all my podcasts so that the “sound coloration” is (mostly) uniform between .5 and -.5. That is the “goldilocks zone” of my audio edits. Not too loud, nor too soft. Nothing clipped.

Amplify or de-amplify in 2.0 decibel increments until you hit that sweet spot of sound.

Cutting sound:

          When I record sound there is usually the setup of the guest(s)' microphone level tests. And when I am finished recording the podcast, I record 20 seconds of room tone (silence). Once you have filtered for noise, you can delete that portion. Trimming the mic-test (start) and room tone (end) is called “topping and tailing.”

Filtered Audio:

• Topping: place your cursor just before the start of the audio you are keeping.
• Wipe left to select the portion being excised.
• Delete.

• The remaining audio is automatically moved to the timeline of 0.0 seconds.
• Tailing: at the end of your recording, place the cursor at the room tone audio and wipe right.
• Delete.

• Now your final edit is ready to export.

Exporting edited sound file:

• Pull down menu>File>Export.
• Export as MP3 – preferred, compressed file that loads faster from social media or web-based listening platforms like WordPress pages or Spotify.
• Export as WAV – larger file that is more in line with CD quality. Not as ideal for online listening/streaming because of the time it takes to load on listening devices.

Time-shift, Fades & Auto-Ducking

If you want to add a music intro or outro to your podcast, it is very easy to do using Audacity. This is known as auto-ducking. Because you "duck" the music below the talk.

• File>Open>select music .mp3 from computer folder. Music always goes on top. Music will be in stereo (2-track).
• Note: Most commercial music imported to Audacity is too loud, re-amplify the gain to be "between the fives" as shown above.
• On pull down menu Tracks>Add New>Mono Track.
• File>Open>name of your podcast.mp3. It will open in a new Audacity work form.
• Select the podcast audio: Command-A (Mac); Control-A (PC).
• On the previous Audacity work form, paste (Command-V or Control-V) onto the Mono track.

 

When using music to embellish a podcast, it is common to start with a short snippet of music first.

The music should be mostly instrumental (you want to avoid voice on voice). Something upbeat and jazzy. Not too long, about 10-15 seconds at normal volume, then we “duck” the music beneath the discussion. We’ll also fade-in the music at the very beginning.

Notice on the graphic above: the “grabber” hand tool. That allows you to slide the track audio along the time line. This is called time-shifting.

For the purposes of this demo: I shift the mono voice to the 10 second mark. Next, on the stereo track, I select the first 5 seconds of music intro.

• Effect>Fade In.

Notice how the audio goes from zero amplification to a phased crescendo of normal volume.

Now let us auto duck the music under the voice. I don’t recommend this for the entire podcast.

It is more for coloration than listening experience. In this example we will do 30 seconds. Best practice is not to duck music beyond your podcast introduction.

• Select the portion on the stereo/music track that corresponds to the mono/voice track being ducked.
• Effect>Auto Duck

 

• Notice how thinned out the music is. Play it back. If the music clashes with the voice, either repeat the effect or go to Edit>Amplify to lower the gain in -2 db increments.
• Delete the rest of the music track and your podcast will commence.

***

Now let's do a fade out. At the end of your podcast, add a music track at the end of your vocal audio. Let it play at normal volume for say 10 seconds. Delete the stereo music after 15 seconds.

Then select from 11 sec.-15 sec.

Effect>Fade Out. It will fade to silence. Consider auto ducking as you do your thank you's and then go to fade.

Conclusion

Audacity is a very robust sound editor, free to use and has a shallow learning curve. If anything in this LibGuide doesn't make sense or you want feedback/assistance on your soundfile, reach out to me at robert.nelson@utah.edu