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Creating an Audio Podcast

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Summary

An introductory guide to recording an audio podcast on a computer with a microphone and free open-source software.

This advice document will help users with little or no experience of recording audio to record their voice onto their computer using free software and simple peripherals. It then covers basic processing and editing of their recording and mastering it to a final format - in this case MP3. Simple instructions are then given for delivering this recording as a podcast through an institution’s VLE and for archiving projects.

Suitable material for podcasting

Podcasts are ideally suited to presenting a series of audio and/or video recordings connected by a common theme and delivered at regular intervals, or a longer recording chopped up into bite-size ‘episodes’. They are often described as being ‘like radio shows’. While this is a useful analogy it is not completely correct, as podcasts can - in the broader sense - include a visual and/or text element as well as audio. In the context of this beginner’s guide, however, we will assume an audio-only podcast.

Podcasts are ideal for providing audio versions of course material for students, and as such are of particular value to visually impaired learners, but they can also help engage students less able (or less motivated) to attend lessons and lectures or to read course material, and provide them with support in a palatable and easily digestible form.

What is a podcast ?

To begin to explain the nature of a podcast, I’ll begin by clarifying what a podcast is not. A podcast is not in itself a file format, nor is it a special type of audio or video file. It is rather a method of delivery - via the internet, or an internal intranet - for these types of media. Most digital audio and video files (or indeed any type of file) could theoretically be delivered as a podcast, but the popular form is an audio or video resource which has been recorded as (or divided into) short episodes, then compressed to be compatible with the intended playback device(s) and posted on a web server.

Users can ‘subscribe’ to a particular podcast series, either with a media player program such as iTunes or Juice, or an RSS reader within their browser, and then every time the podcast is updated by its author with new material subscribers will be notified of the posting of a new episode and can choose to download it. Some podcast clients (Apple iTunes for example, the most popular podcast client, which is available free for Windows and Apple OSX) can be set up to check for and download new episodes automatically, as soon as they become available.

Once the episode is downloaded, podcast subscribers can then watch or listen to their new content on their computer or transfer it to a mobile device (eg an iPod - hence the origin of the term ‘podcast’) to listen to on the bus, at the gym, or wherever. Again some podcast clients have the ability to update mobile devices automatically upon connection to the host machine, and indeed some newer mobiles can even download podcasts directly from the internet, bypassing the computer completely.

Getting started, and making a test recording

To make an audio recording on your computer you will need some appropriate audio software, a microphone, and some means of listening back to your recording (ideally some good quality headphones). For our purposes a free, open-source program called Audacity will be ideal for recording duties. It is widely available for download from the internet and compatible with most PC systems. Its features are quite basic but it will allow recording of multiple audio ‘tracks’ which can be edited and then played back simultaneously, mixed together, and rendered to a standard stereo mp3 file, which is what we intend to do now:

Install Audacity on your computer (or an equivalent audio recording package of your choice). Download and install the LAME MP3 encoder which will allow you to export your final podcast from Audacity as a compressed mp3 file for easy distribution. If you are using a different audio program of your choice, ensure that it is similarly enabled.
Plug in your microphone/headset - your computer should automatically recognise the device and install any necessary software drivers. Drivers enable the computer to communicate with a device and to understand its commands, and are usually included with a USB device, or available from the manufacturer’s website. Many USB microphones are now simple plug-and-play, and will install their drivers without further intervention, on connection to the USB port. Either a USB headset or microphone will connect directly to the computer via a USB port, bypassing the system’s soundcard completely. This ease of set-up is the main reason we recommend these devices for your initial sessions.
Position the mic on a small stand on a desk or table, or on a floor stand if you prefer, at a short distance from the speaker. 5-30cm is ideal, generally the closer the better, as long as the speaker is comfortable [although be aware of the proximity effect at very short distances]. If you are using a headset, you clearly don’t need to worry about this step, as the mic will be on the end of a small arm attached to the headphones. If you are using a separate USB microphone, place it on a stand which places it on a level with your mouth in either a sitting or standing position - your preference.
If you are using separate headphones, plug them into the headphone output of the computer audio interface (soundcard), and adjust the volume to a comfortable level, starting from zero. If you are unsure how to adjust your audio settings, they are typically accessible from Start>Control Panel>Sounds and Audio Devices on Windows, or System Preferences>Sounds, and the Audio/MIDI Setup application (in your Utilities folder) on Apple Mac OSX. If you have a music track with which you are familiar on your computer, then use this to test your headphone connection.
Launch Audacity (or equivalent), and check that your microphone is selected as your input device [Audacity’s menu path is: Edit>Preferences>Audio I/O>Recording>Device: ‘name of your microphone’] and set it as a mono source [Edit>Preferences>Audio I/O>Recording>Channels: 1 (Mono)]

What you will now see is the main project window. Most audio workstation programs work on very similar principles, and Audacity is no exception: a toolbar and time-line at the top, then below it one or more audio tracks, running parallel to each other, each with its own level (volume), pan (L-R balance), and a graphical representation of the sound wave, over which the ‘play head’ - a vertical line - will travel left to right as you move through your track, indicating your position within it.

Audacity annotated screengrab

Press the record button on Audacity’s transport, and speak into the microphone (testing, testing ... one two one two ... Mary had a little lamb, etc) at a natural volume, with one or two louder words, and a couple of sibilant (‘s’) and plosive (‘p’, ‘b’) consonants. Press stop. Return the transport to the beginning, and press play.You should hear your recording, and see a depiction of its audio waveform, running horizontally; if not, check connections, and that your mic and headphones are selected as your input and output devices respectively.

Listen back to your voice. If you hear distortion, then your level is too high, and you should reduce the input level (there is a slider next to a microphone icon at the top of the Audacity screen to control microphone input level), or move further away from the microphone. Similarly, if the level is too low, turn it up, or move closer, as amplifying too quiet a recording at the mixing stage will also amplify any background noise (hiss), as well as sounding more “grainy” and low resolution. You can use the level meters in Audacity to visually gauge input levels.

If plosive consonants make a ‘popping’ sound (caused by the pressure wave they can produce when hitting the microphone pickup) then you should use a popshield. These are commercially available, or you can fashion one from coathanger wire bent into a circle a few inches across with fine stocking material stretched over it, and placed an inch or so in front of the mic.

Once you are happy with the level and sound, do a couple more practice takes, until you feel comfortable with the microphone.

Planning

Write some notes outlining your podcast episode and run through them, speaking aloud to get a feel for the ‘script’ and an idea of its length. You don’t need to write it out word-for-word, though if you plan to provide a text transcription this may be useful. Speak in your normal voice, and try neither to rush nor to speak too slowly - just act natural! Time yourself; as a guideline, podcast episodes of around 5 minutes will give you time to get into your subject, but won’t run on and risk losing the attention of your (YouTube generation) audience. Clear, concise episodes will maximise the impact of your material.

Recording

Ensure that there is no background noise (hoovering, TV etc.) coming from adjoining rooms, pour yourself a glass of water, and settle down in front of your microphone with your notes. Sitting down may be more comfortable, but standing up allows for better breathing and a more dynamic approach - choose whichever suits you better or feels more natural, or try both and listen to the differences. Press record, leave a few seconds ‘lead-in’, then begin speaking. Again, take your time and stay relaxed - if you are unhappy with your first take, you can do another, so there is no pressure. It can help, in the absence of an audience, to imagine yourself explaining your material to an attentive listener.

If you make a mistake, cough, etc. you don’t necessarily need to start again. Just wait a few seconds, then carry on from a point shortly before the mistake, and you can edit out errors later (see below).

When you have finished, leave a few seconds of silence, then press stop. When you have captured a successful take, you can begin to prepare it for delivery.

Editing

If you have managed a single uninterrupted take, then you may not need to do any editing at all - well done! If you coughed, or made a mistake which you wish to edit out, then this is the simple method for doing so:

Inspect the waveform of your recording within Audacity, and find the offending glitch in your otherwise perfect performance. You may need to use the zoom tools to get a closer look, which all look like icons of a little magnifying glass, and have various fairly self-explanatory functions. Clicking on the waveform display with the selection tool will enable you to jump to different points in the recording for a quick listen, to find the section you want. If you have left gaps after any mistakes - as recommended - this should make identifying them by inspection of the waveform easier, as you will notice portions of silence as flat sections in the waveform. You can add labels at any point, to mark sections for editing or reference, by using the Project>Add Label menu commands. Once you have established which section of the waveform needs removing, choose the ‘selection’ tool (top left corner of the toolbox) and click and drag across the unwanted section to select it. It will be highlighted in grey. Now choose Edit>Delete, and the selected section will be removed, and the two sections either side of it will be joined together.

If there are unwanted variations in level (volume), or if you wish to fade in at the beginning and fade out at the end, then you can use the ‘envelope’ tool to automatically change the volume of each track as it plays back. As you use it to add level automation points, the waveform display will change to reflect the variations in volume over time. These automation points can be picked up with the mouse and moved around until you achieve the desired effect.

These are probably the only tools you will need to use to perform basic editing. Audacity’s editing, in common with most audio programs’, is non-destructive - i.e. the original recording is not altered by the editing procedure, but merely the order in which it is played back. If you get a bit over-enthusiastic with your editing, you can always fall back on the trusty Ctrl+Z (Undo), or the toolbar Undo/Redo buttons, which will cycle you backwards and forwards through the undo history an unlimited number of stages since the document was last opened. This can also be a handy way of trying out edits or effects.

For further editing tips, refer to Basic Audio Editing.

Adding music and sound effects

Incidental music and sound effects can add depth and a professional sheen to your podcast. They can help set a mood, demonstrate or reinforce a point, and effectively ‘bookend’ an episode. For example, you could add short sections of recorded native dialogue or music to a language lesson podcast, or a suitable atmospheric soundbed to a history lecture.

Most audio software (including Audacity) will allow additional tracks of music and effects to be placed alongside the master narrative track. Music and effects can be automatically faded in and out with the ‘envelope’ tool, as explained above, and their individual levels set with the volume slider in the tool panel at the left hand end of each track.

N.b. - Care must be taken to observe copyright restrictions of any additional music, sound or video resource not produced by yourself. If in doubt, do not use it! There is a significant amount of royalty-free music and audio material available for educational use under Creative Commons terms. Some internet browsers (eg Firefox) include a Creative Commons search function, selected from a drop-down list at the end of their search box:

Creative Commons highlight

Creative Commons material can generally be used free of charge for non-commercial purposes. Many producers of this material simply ask that users credit them for their work, so be sure to list composers/producers where requested, and check terms of use.

You can add any WAV, MP3, Ogg Vorbis, AIFF or AU audio file to your Audacity project, by using the Project>Import Audio menu command, and then selecting the relevant file. A new track will be automatically created, whose level you can again control with the track volume control and ‘envelope’ tool. Use the ‘Time Shift’ tool to move the audio into the correct synchronisation position with the voice track. You can add multiple additional audio tracks for different music and effects, and they will all be ‘mixed’ at their respective levels when you come to render your final mix.

Exporting an MP3

When you have your track sounding as you want, you are ready to render it as a stereo mix, suitable for distribution by podcast. We have chosen MP3 as the podcast file format as it is familiar to most users, compatible with almost all devices, and offers a wide range of compression settings, as well as rich metadata.

In Edit>Preferences>File Formats you can select the bitrate (quality) for the exported file. The higher the bitrate, the better the sound quality, but the larger the file size. A bitrate of 128kbps will usually give perfectly acceptable sound quality for most uses, with a relatively small file size - approximately 1Mb per minute. You can experiment with lower bitrates for even smaller files, but the compression artefacts begin to become quite audible. Variable Bit Rate (VBR) encoding allows the software to alter the bit rate it is using to suit the complexity of each section of a file, and can afford significant additional filesize reduction, while allowing higher bitrates for more dense sections. Try using VBR on your material, and compare the results to a fixed bitrate version.

To export, go to File>Export As MP3 and choose an export destination.

Adding Tags (Simple Metadata)

MP3 files allow the inclusion of extensive additional information about the origin and nature of the audio content. This information is called ‘metadata’, and in an MP3 takes the form of ID3 tags. These are the same as the tags which media players use to tell you the artist, album, year, track number etc of a commercial MP3.

You may want to add some of these tags to give information on title, production dates, authorship, ownership, content, genre etc. of your audio. If you want to begin adding this metadata at the production stage, then before you export your mix from Audacity, go to Project>Edit ID3 Tags and enter whatever information you want packaged with your audio into the fields provided. Including metadata at this stage will help you keep track of your audio catalogue in the future, and it is always worth spending a few minutes on it - you may remember a project’s details now, but in a month’s time maybe not!

Audacity ID3 tag editor

Alternatively, your ID3 tags can be added or edited later in more depth within an audio player such as iTunes. Open iTunes and right click on the file, and choose ‘Get Info’. The window which opens will allow you to edit what additional metadata, and even artwork, you package with your mp3.

Delivery by VLE

The most common VLE platforms - Blackboard and Moodle - do not include native features to allow podcasting, and require the addition of third-party plugins (such as Podcast LX and Wimba) to offer true podcasting - i.e. a subscribable RSS feed. If your VLE does not have podcasting facilities (which you can verify with your IT support team), or you prefer a simpler tool, then there are other options open to you for delivering audio recordings such as our MP3 - chiefly a simple ‘File Download’. Some analysts argue that advertising a file as available for download is just as effective as podcasting for reaching the desired audience, so don’t let the absence of a special podcasting module on your VLE discourage you from producing support materials in audio and video formats - there are perfectly valid alternatives.

Podcasting

A podcast presents your audio file within an RSS (Really Simple Syndication) feed, which actively pushes out information about added content to subscribers. Once students have subscribed to your podcast RSS feed, then new course materials will be automatically flagged for students’ attention as they are added to the podcast. This obviates the need to announce every new addition to the course documents list. In practical terms this means that if at the beginning of a course all of its members subscribe to that course’s podcast feed, and instruct their computer to check regularly for updates, then all materials added to this podcast at any later date will be immediately announced and made available to all subscribers through their media player (iTunes or similar). As such podcasting is a more reliable method of notification than email, which can sometimes get overlooked in a busy inbox!

File download

You can - in the absence of podcasting facilities - make your audio recording available to students as a simple download, a basic feature supported by all VLEs (although some have limits on file sizes, so be aware of this when choosing your MP3 bitrate etc). The quality and format of students’ downloads will be identical to audio files acquired by podcast subscription. As noted above you can email course members to inform them of the availability of new online materials, and if you include a link to the relevant page on your VLE in your email then they can simply visit the appropriate course content area and download the new audio file(s) manually.

For either method of delivery you will need to sign into the relevant course with your instructor credentials and select the Content Area where you wish to publish your audio material. In Blackboard, switch to ‘EDIT VIEW’ and add a new item with the +Item key or Select>Podcast Episode>Go, depending on whether you intend to add a file for download or deliver it as part of a podcast series, and upload your MP3 from your computer.

Which method you choose is of course up to you, but longer-term maintenance of a podcast will be easier and its use is more readily scaleable, though initial setup and technical requirements can be a little more demanding.

Archiving your Projects

As well as exporting the final mix to mp3 it is wise to archive the complete Audacity project as well, which will include all the separate recorded files, edits etc. Should you wish to go back to create a more high-quality mix or one in a different file format, add effects, or re-use the audio material in its raw form for any other purpose, you can simply re-open the project and continue from where you left off. Create a folder for Audio Projects in My Documents, and save your Audacity projects to it, which will use the .aup file extension.

Bear in mind that the Audacity project will store all recorded files at their original quality and may therefore be quite large! For long-term archiving, you may want to copy these projects to an external drive or burn them to data DVD, allowing you to erase them from the computer hard disc to free up space.

Equipment Notes

The Suggested Equipment list below constitutes a basic set-up to produce what we would consider acceptable audio quality, but you can substitute any element if you are confident to do so. For recording software we recommend Audacity as it is well established, popular, free and cross-platform, but you can of course use alternative audio software of your choice. If you have a recent Apple computer you may prefer to use Garage Band, which is included free with later versions of Apple’s OSX operating system and offers many additional features designed for podcast production as well as video podcasting and soundtrack creation features. There are alternative Windows programs such as Reaper.

Many external soundcards include free ‘lite’ versions of commercial audio recording packages which will often offer excellent features perfectly suited to our purpose. Many are also available in downloadable evaluation versions should you wish to experiment, though some may have a limited evaluation period before requiring purchase, so read the terms carefully. As long as you can render and convert your final recording as an mp3 audio file then the specific program you use is largely immaterial, and a matter of personal preference. Contact our sound support team if you would like further advice.

We recommend a USB microphone purely for simplicity; many cheaper microphones are available which will plug into your soundcard mic input, and will give mixed results. Many home PC soundcards have acceptable playback quality but poor recording quality, and a USB mic will usually be superior unless your PC has an upgraded audio interface. The microphone inputs on most Apple computers are generally of acceptable quality. If you do intend to use a separate microphone and soundcard then as long as the relevant drivers are installed for the interface all other sections of this guide will apply unchanged.

Suggested Equipment

Mac or PC with a suggested minimum 1GHz processor, 1Gb RAM (2Gb+ preferable) , 1Gb+ free hard disc space, a headphone output (if not using a headset), and free USB port. Windows XP/Vista, Linux or Mac OSX operating system.
Audacity audio recording / editing software with LAME mp3 encoder plugin [Audacity and LAME are free and open source for all platforms] or Garage Band [Mac only].
USB microphone (eg Rode Podcaster, a high quality, though more expensive option), or USB headset (headphones and microphone combined - a simpler and cheaper option, though more basic in sound quality) such as the Sennheiser PC166, or one of the Logitech ClearChat USB range. All of these devices have built-in USB audio conversion, and either headphones or a built-in headphone output, so do not require a computer soundcard at all.
Headphones (if not using a headset)
Pop Shield
iTunes media player and podcast client

Audacity(R) software is copyright (c) 1999-2008 Audacity Team.
Web site: http://audacity.sourceforge.net/. [It is free software distributed under the terms of the GNU General Public License.]
The name Audacity(R) is a registered trademark of Dominic Mazzoni
Audacity does not distribute LAME MP3 encoders, but Audacity can link to third-party LAME libraries for MP3 encoding subject to the legal precedents for software patents in the country of use