Speeding up Podcasts part 2:
Using Audacity to speed up MP3s

Part of the Faster Podcasts Series

  1. Speeding up podcasts:
    Listen to more, faster – Part 1
  2. Speeding up Podcasts part 2:
    Using Audacity to speed up MP3s
  3. Speeding Up Podcasts part 3: Make Yourself an Audiobook

faster podcast

I established in the previous article that with all the interesting content out there, it can be quite daunting to listen to all those great podcasts. The ease with which iTunes lets you discover, subscribe to and manage podcasts can quickly lead to an overwhelming number of episodes and timespan to get through. "Podcast Overload" is a very real possibility.

I also noted in that article that Apple’s Quicktime Player application can be used for faster playback… if you happen to be sitting at a computer. But what if you want to take advantage of the "pod" part of a "podcast" and listen on-the-go?

Luckily for us all, there are a couple of ways to speed up your spoken word audio before you pack it up and take it with you. Specifically, there are two main approaches, and each has its advantages and weaknesses. The first method involves using an audio processing program to decrease the total running time of a podcast before copying it to your iPod. Alternately, if you have an appropriate model (4G and later or any Nano), you can format your files so that the iPod itself adjusts the playback speed in real-time.

This approach has two principal advantages:

  1. Flexibility: Audio processing gives you the greatest amount of control over the final playback speed of your podcasts. Speed it up by 10% or 200%, whatever works for you.
  2. Organization: Because you are editing and replacing the original downloaded podcasts, you can maintain the organizational functionality present in iTunes + iPod.

However, this approach comes with trade-offs:

  1. Processing time. Running an audio file through a sound editor takes time. If you want to increase the playback speed, you have to run it through the processor before dropping it onto your iPod.
  2. Potential Zero-sum changes. Whether a project is even worth attempting depends on the likelihood of a net gain in time. If it takes you 5 minutes of computer use + processing time to shorten audio by 4 minutes, then you would have been better off just listening to it in the first place. This consideration is increasingly relevant for older computers with slower CPU speeds and longer processing times.
  3. Inflexibility. Ironically, the other disadvantage of this approach is inflexibility. Once you’ve processed the file, you’re stuck with it. If you’ve happened to set the speed to a rate that is uncomfortable or impossible to listen to, then you’ll probably have to re-download the podcast and try again.

audacity icon

Bearing all that in mind, just how does one speed up a podcast? Easy: Audacity, an open-source audio program that’s packed with features, cross-platform, fairly simple to use, and of course, free. In fact, the program is most likely used in the actual production of many of the podcasts you’ll be modifying.

Additionally, you’ll need the LAME mp3 encoder to save your processed files back to mp3 after Audacity is finished with them.

Audacity also supports batch processing (called "Chains" in its parlance) that allows you to open multiple files, run filters, and save back to mp3 with just a couple of clicks. Not bad, but how’s it work with iTunes?

In basic form, the workflow looks like this:

  1. Podcast is downloaded. MP3 file is saved into your iTunes Music > Podcast folder and the appropriate entry appears in iTunes’ Podcast panel.
  2. Said mp3 file is opened in Audacity. Modifications are made.
  3. New, faster mp3 file is exported.
  4. Original mp3 is replaced.
  5. iTunes entry is updated with a shorter playing time.
  6. Profit?

Alright, now that we know what we’re in for, let’s walk through the procedure.

Install and Configure Audacity with LAME mp3 encoder

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Download Audacity and LAME encoder for your system. Version 1.3 (beta) is required for batch/chain processing.

Now to configure.

Once Audacity is installed, we need to tell it where the LAME encoder is. So, launch the program and select the Preference menu item. Under the file formats section, choose "Find Library" next to MP3 Export Setup. Also, choose the bitrate to save your modified podcasts at. Most podcasts are published between 64kbps and 128kbps. In my experience, 64kbps provides sufficient quality for listening to spoken word, though you should adjust it to fit your preference.

Next, we just need to set up a Chain. Chains are like scripts inside Audacity that automate a string of operations. For our purpose, we need to build a chain that imports the mp3, changes the tempo, and re-encodes it back to mp3. It’s really easy, so let’s get it set up.

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  1. From the File menu, select "Edit Chains." You’ll be presented with a box showing the pre-configured Chains.
  2. Click "Add" and give the Chain a name (ex: 25%Faster)
  3. Then click "Insert" to add a step to the process. You don’t need to tell the Chain to import a file. That happens automatically when you run it. So the first thing to do is select "Change Tempo" not Change Speed. Change Speed will affect the pitch of the audio, like speeding up a cassette tape or turntable (aka "chipmunking"). Change Tempo leaves the pitch as it is.
  4. In the Parameters field, enter to amount to speed up by. 20% will result in 48 seconds for every 60. 200% will result in 30 seconds for every 60.
  5. Next, click Insert again and select "ExportMP3." That will complete the Chain.
  6. At this point, you can create multiple Chains for different speeds if you want. One for 15%. One for 50%, etc. When you’re done, close the Chains window.

Two steps, that’s it. Change tempo -> ExportMP3.

Let’s Get Speedin’

Now that Audacity is all set up, we can do the actual processing.

  1. From the File menu, select "Apply Chain" and select the one you created earlier. Click "Apply to files."
  2. Navigate to where your podcast files are stored. Unless you’ve changed your iTunes settings, they’ll be in your "iTunes Music" folder, in a folder called "Podcasts."
  3. Select the files you want to speed up. On a Mac, hold down the Command/Apple key to select more than one file. On Windows, use the Control key.
  4. Click "Open." Audacity will begin processing the files. When it’s finished, you’ll see a folder called "cleaned" with your originally downloaded files. Inside that folder is your shiny new faster podcasts.
  5. Move the new files out of the "cleaned" folder. When asked if you want to over-write the existing files, say yes.
    IMPORTANT: If you want the option of re-processing the files at a different rate, copy or duplicate (don’t just move) them to another folder before replacing.
  6. Open iTunes and click on Podcasts from the source view. Select the episode that you modified. The time should change, but if it doesn’t, get info on it. That will force iTunes to refresh the display.

podcast before and after

Ta-da. Welcome to the world of faster podcast listening. The next time your iPod is updated, the new faster podcasts will be copied and you can take them on the road.

Speeding up podcasts:
Listen to more, faster – Part 1

Part of the Faster Podcasts Series

  1. Speeding up podcasts:
    Listen to more, faster – Part 1
  2. Speeding up Podcasts part 2:
    Using Audacity to speed up MP3s
  3. Speeding Up Podcasts part 3: Make Yourself an Audiobook

faster podcast

The first in a multi-part series dealing with speeding up the play rate of podcasts so you can listen to them faster and fit more subscriptions into your schedule. Part One: The problem at hand and a simple computer-based solution.

UPDATE: Toward the end of this article, I point to some scripting techniques to automate the acceleration of podcasts with QuickTime. Well, Mac users, it’s your lucky day because I went ahead and complied an AppleScript that opens a selected podcast in QuickTime Player and allows you to set the playback rate. I’ve taken to calling it PodFast. Download it.


After about a year on hiatus, I recently got back into the swing of listening to podcasts. The podcastosphere has exploded in the past twelve months and beyond old favorites such as Sound of Young America and EscapePod, everyday seems to introduce me to new, awesome content. There’s Grammar Girl’s writing tips, and Darker Projects’ Section 31 adventures, the WordPress community podcast, foreign languages, and NPR as well as many more news, education and entertainment podcasts. Heck, even the U.S. Department of State has a podcast.

With all that good stuff, it’s easy to become a podcast junkie at the expense of your music, books, magazines, TV, movies, pets, friends, family and career.

With each compelling episode, you crave more and more, to the point where they start to seriously suck up your time. While some, like Grammar Girl’s, only run about 5 minutes, the average length of a podcast episode ranges from 20 to 40 minutes. Some podcasters are aware of the time burden that a podcast can create, but even those who try to produce short episodes tend to drastically underestimate the amount of time needed to convey all the info they wish.

Solution: Speed it up.

Most recorded media can be sped up by a few percentage points without any perceptible change. Depending on the particular characteristics of the sound, podcasts of spoken word can usually maintain their intelligibility at significantly higher increases. The iPod’s built-in accelerator increases playback in real-time by 20% without changing the pitch or interfering with the ability to understand what is being said (though it does falter when dealing with low, muffled voices).

That’s great if you happen have a later-generation iPod. But not everyone does, so I would suggest to all podcast producers that time compressing your episodes by 5-10% has its benefits. For podcasters there’s smaller files and less bandwidth used, and subscribers enjoy faster downloads and shorter listening times.

While some podcasters might adopt that practice, it is probably never going to become widespread. So lets us take an end-user centric approach. What solutions exist to speed up a podcast once it is downloaded?

Computer-bound playback

quicktime logo
A lot of people listen to podcasts while sitting at their computer. The iTunes program itself, unfortunately, has only one speed: normal. When you press play, what you hear is what you get. You’re stuck with whatever the podcaster uploaded, whether it’s spoken with perfect tempo or with an agonizingly slow drawl. There’s just no option to adjust the speed on either a global level or for individual tracks.

QuickTime Player however, does allow you to easily change the playback rate in real-time. You can speed through filler material as effortlessly as you can slow down complicated sections (especially useful for foreign language podcasts). QT Player has the additional advantage of supporting video podcasts, so you can adjust the play rate of those as well. Currently, no portable player can do that.

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To open a podcast file in QuickTime Player, select its entry in iTunes’ Podcast panel. On Mac OS X, select “Reveal in Finder” from the File menu (command R). On Windows, select “Show in Windows Explorer” from the file menu (control R). You can then drag the mp3 to QuickTime Player.

QuickTime is required by iTunes, so if you have it installed, then you already have QuickTime. To access playback options, select “Show A/V Controls” from the Window menu.


You can streamline the process of getting the files into Quicktime by using some of these scripting techniques at MacOSXHints.com. They include ways to automatically set the playback speed when the file is sent to QuickTime and increase the file’s play count so that iTunes will continue to download fresh episodes. It’s mostly AppleScript for the Mac, but there is one JavaScript for Windows option.

If you use iTunes to manage your podcast subscriptions and downloads and do most of your listening while working at your computer, then QuickTime is pretty much the most simple, best way to speed up that process.

But what if you use an iPod or other mp3 player to make your podcasts portable? There are a couple methods for accelerating your listening on-the-go. Try this one.