Podcasting for E-Learning: Setting Audacity Preferences

Setting Audacity Preferences on Your Computer

Before beginning a recording project in Audacity, it's necessary to configure your version of Audacity’s preferences in the Edit Preferences dialog box. This ensures that the sound source and playback options are set correctly as well as bit-rate, quality indicators and so on. Follow this step-by-step procedure to configure Audacity for your computer and operating system.

Configuring Audacity

You Try

1. Launch Audacity
2. Check the Preferences.
   Checking the Audacity preferences is very important step and should be done before you begin editing any audio. You can locate the Preferences Dialog box by going to Edit Preferences, or the shortcut key combination CTRL+P.
   
3. Set Audio Input & Outputs.
   Select the Audio I/O tab from the choices across the top of the Preferences Dialog box. I/O is short for Input Output and is where you’ll tell it to record your sound from and where to play it back.
   
4. Set Playback Output.
   
   
   From the Playback Device: drop-down menu, select the output device that you would like to route the sound through. In this case, I’m sending the signal via my internal PC sound card.
   
5. Set Recording Input.
   
   
   From the Recording Device drop-down list, select the sound source you want to record from. In this case, I’m selecting the SigmaTel sound card, which takes input from the microphone that I’m going to use to record some voiceover narration.
   
   
   If you’re recording music, select the Record in Stereo check box. If you’re just recording voice-over narration, leave it unchecked. Similarly, uncheck the "Play other tracks while recording new one” option (unless you’re Les Paul or Mary Ford).
   
6. Sound Quality Tab.
   
   
   The Quality tab is where you’ll set the quality of your audio. The higher the sample rate, the better quality your audio, but the larger the file size will be. For CD quality sound, record at 44,100 Hz. You’ll typically leave the other settings at their factory defaults.

More…

Podcasting for E-Learning – Tour of Audacity’s User Interface

In my previous post, I discussed interface metaphors, and showed a video example of the process behind the analog tape-editing metaphor used by most media editing tools - including Audacity. Today, I will describe how this approach to editing is replicated virtually, via your computer's user interface. Figure 1 shows the primary menu options and functions of Audacity.

Figure 1 The Audacity UI
[Click to Enlarge]

The menu bar contains all of the functions for Audacity.

Figure 2 The Audacity Menu bar
[Click to Enlarge]

You’ll see some familiar features – Open, Import, Copy, Cut, Paste, and so on. There are also a range of audio-specific functions including the facility to analyze the audio signal, generate white noise, a pure note tone, or a click track, as well as a range of audio effects including:

• Noise reduction (NR) to remove background noise
• Normalization (increasing or decreasing the amplitude of an entire audio signal so that the peak amplitude matches a desired target. Typically, normalization increases the amplitude of the audio waveform to the maximum level that does not introduce any new distortion – this “makes the audio louder”
• Equalization (EQ) - changing the characteristics of the audio – i.e. add bass or treble, cut or enhance certain frequencies

The features of the Audacity timeline (see Figure 3) are common across all audio editors.

Figure 3 The Audacity Timeline
[Click to enlarge]

1. The label track enables you to insert information about events on the timeline. Here, I have indicated the point where the intro music begins, and the point where the first voice-over should start.
2. Most important is the audio waveform itself. The waveform is a graph showing the amplitude (loudness) of the audio signal over time.
3. The track controls allow you to control the characteristics of an individual track on the timeline.

There are two types of audio file in Figure 3: a stereo file which is typically used for music, and a mono file, which we use for narration. There is little point recording voice-overs in stereo – you only have one voice (or audio source), after all. If you record a voice-over in stereo, you only double the file size, for no gain in quality.

Using Audacity

These are the Rules of Audacity (according to SourceForge.net)

• One audio clip per track.
  An audio clip is simply a piece of audio material, imported, recorded, split or duplicated from another track, one track can only carry one piece of audio at a time. You can extend it by pasting material or inserting silence in to it, or cut a piece away, but it will always be one continuous piece of audio.
• Audacity always records to a new track.
  This new track is opened at the lowest free track. You'll can zoom out and then resize the track view of the lowermost-most track to see what is recorded. You can actually use the window sliders at the bottom and right to do this after starting to record, but this way no performance will be lost to the windowing system.
  Pressing CTRL+F displays all the tracks in your entire project. Note: this function only affects the horizontal zoom (left-right zoom); you must use the mouse and the magnifying glass icon to zoom out .
• Edit/Duplicate will not create a new audio file.
  This may not seem important, but it is useful to know this if you're editing a large recording. Audacity is a non-destructive editor (unlike the analog editing process): it works by referencing the original (or master) audio material: edits and other change you make affect the referenced file, not your master file.
  
  One of the positive consequences of non-destructive editing is that you can undo/redo edits as many times as you need to even after you have saved your project, which is pretty cool.

Next Time: Setting Audacity Preferences

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Podcasting for E-Learning: Audio Editing + Audacity

Previously in this series of E-Learning Curve Blog posts about Podcasting for E-Learning, I discussed downloading and installing the open source audio editor called Audacity. I chose Audacity because it’s free (as in speech), it’s available for Linux/Unix, Mac OS and various Windows operating systems, and most importantly, it’s a very impressive media editing tool.

If you’ve taken the time to install and run the app you should see something similar to Figure 1: this is the Audacity audio editor user interface (UI) in Windows XP.

Figure 1. The Audacity User Interface
[Click to enlarge]

If you’re not familiar with digital media production, this type of UI can seem quite daunting, and even alien. Today, I’m going to begin normalizing this new environment for you.

Now read on…

I’ll begin by taking a step back for a moment: let’s discuss interface metaphors.

An interface metaphor is a set of unifying concepts used by a computer graphical user interface to help users more easily interact with the computer. The interface metaphor treats the monitor of a computer as if it is the user's desktop, upon which objects such as documents and folders of documents can be placed. A document can be opened into a window, which represents a paper copy of the document placed on the desktop. Since it was first developed at Xerox PARC in 1970, the desktop metaphor has been extended and stretched, so that items not found on a 'real' desktop (like a trash can) are now displayed onscreen.

In this context, we can say that pretty much all digital editors have an interface metaphor based on analog tape editing procedures: the waveform (see Figure 2) represents the magnetic tape, and the transport bar (Play, Pause, Stop buttons, and so on) represents an analog tape recorder's transport controls, for example. Similarly, there are Cut, Splice and digital sound effect features and functionality that replicate these processes in the analog world.

Figure 2. Some Audacity features and functions
[Click to enlarge]

In my view, the most effective way to demonstrate these concepts is through an example. In this YouTube video, Rod Summers demonstrates how to edit a piece of analog magnetic tape.

The Scenario:

The source audio is a short piece of recorded voice-over of the presenter counting from one through ten. He has transposed "six" and "five" in his narration. This demonstration outlines the process for correcting the error.

Here are the steps in the process:

1. The editor cues up the tape by using a technique called "scrubbing"
2. He marks the In- and Out points for the edit...
3. And he marks the insertion point for the edit
4. Next, he makes the edit by physically cutting the tape and splicing the join...
5. Before inserting the cut piece of tape into it's new position
6. Finally, the edited tape is played back to test the verify the edit
   
   

Next time: I will look at editing in a digital environment ...and don't worry, this is a much easier undertaking when using a tool like Audacity!

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Podcasting for E-Learning: Editing and Producing Podcasts

So far in this series of posts about Podcasting for E-Learning from the E-Learning Curve Blog, I've covered a lot of material, including:

• A Brief History of Audio in Education
• The Four 'P's' of narration
• Introduction to Audio Production
• Digital Audio Basics

Now, it's time to look in some depth at editing and producing podcast content.

As I discussed last time, non-linear editing applications are media editing tools which can randomly access the source material - and that’s it. You don’t have to edit audio in a beginning-middle-end sequence. You can also drop in new files, split audio, modify the volume (or amplitude), “top and tail” the recording, and add effects, before generating a rendered file which contains all of the modifications you made to your audio.

Non-linear editing enables the editor to access any frame in an audio clip. It can be viewed as the audio equivalent of word processing, which is why the process is often called desktop editing. Typically, audio is either recorded directly to a PC hard drive, or is imported from another source, in the same way as that text is either authored within the a word processor application, or a file is imported from another location.

In non-linear editing, the original source files are not lost or modified during editing. This means that you can easily make changes and cuts, experiment with the audio, and undo previous decisions secure in the knowledge that you are not interfering with the original - or master - files. Loss of quality is also avoided as you don't have to repeatedly re-encode the audio when different effects are applied.

While there are many excellent commercial, free-to-use, and open source audio editing applications applications available, the editor I will talk about during this series is called Audacity.

Audacity is an open source, easy-to-use multi-track audio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems. You can use Audacity to:

• Record live audio.
• Convert tapes and records into digital recordings or CDs.
• Edit Ogg Vorbis, MP3, WAV or AIFF sound files.
• Cut, copy, splice or mix sounds together.
• Change the speed or pitch of a recording.

So, let's download and install Audacity.

You Try:

1. Navigate to the Audacity download page and select the download for your operating system.
   
   
   
2. Click on the appropriate link. This will take you to the SourceForge download page - don't "save link as.." or "save target as..".
3. The SourceForge download should start automatically. If it does not, click the links in the black panel marked "direct link" or "mirror". Only these links and the automatic download are authorized versions of Audacity. Disable any automatic download managers if the download is incorrect.

I also recommend that you download these optional files:

• LADSPA plugins 0.4.15 installer (.exe file, 1.5 MB) – nearly 100 audio digital effects plug-ins
• LAME MP3 encoder - Allows Audacity to export MP3 files

System Requirements: Windows-based Systems

The values in the "Recommended RAM/processor speed" column below are for tasks like recording for an hour, or editing three 20 minute tracks simultaneously. The values in the "Minimum RAM/processor speed" column will be fine for smaller/shorter tasks, especially if unused programs are closed.

Windows version	Recommended RAM/processor speed	Minimum RAM/processor speed
Windows 98, ME	128 MB / 500 MHz	64 MB / 300 MHz
Windows 2000, XP	512 MB/1 GHz	128 MB/300 MHz
Windows Vista Home Basic	2 GB / 1 GHz	512 MB / 1 GHz
Windows Vista Home Premium/Business/Ultimate	4 GB / 2 GHz	1 GB / 1 GHz

Audacity works best on computers meeting more than the minimum requirements in the table above. Where Audacity is to be used for lengthy multi-track projects, Audacity's developers recommend using Windows 2000, XP or Vista running on machines of substantially higher specification than the minimum specs outlined above.

Apple Macintosh

Installation instructions (MacOS 9 and OS X):

1. Inside your Applications folder, create a folder called "Audacity"
2. Double-click the downloaded .dmg to mount it
3. Option-drag the whole of the .dmg contents (not the .dmg itself) into the "Audacity" folder you created
4. Double-click Audacity.app inside the Applications folder to launch it

Mac OS X version	Audacity Version	Recommended RAM/processor speed
Mac OS X 10.1	Audacity 1.2	64 MB / 300 MHz
Mac OS 9.0	Audacity 1.0	64 MB / 300 MHz

Linux/Unix

Audacity's developers recommend using the latest version of Linux/Unix from your distribution that is compatible with your hardware specifications. Audacity will run best with at least 64 MB RAM and a 300 MHz processor.

Installation packages for Audacity on GNU/Linux and other Unix-like systems are often provided by individual distributions:

• Alt Linux
• Debian
• Fedora Core
• Fedora Project
• Mandriva i586
• OpenSUSE
• Red Hat
• SuSE and packman (suse)
• Ubuntu: packages.ubuntu and rpm.seek

This list is not comprehensive. If you don't see an up-to-date package for your distribution, search your distribution's web site for the latest information. Alternatively, you can compile Audacity from source code.

More…

New E-Learning Curve’s Other Podcast new episode release:

Transatlantic: The Flying Boats of Foynes. The Complete Podcast Documentary.

It's the 70th anniversary of the first scheduled trans-Atlantic air passenger service, which opened in July 1939. Told against a backdrop of the momentous events of World War II, this podcast documentary tells the story of the town of Foynes on the River Shannon in Ireland, which served as the western European base for the majestic flying boats of Pan Am, Imperial Airways and other airlines in the Golden Age of Aviation.

From their proving flights in the late 1930's through World War II and into the post-war period, Chief of Launch Operations at Foynes recalls his time working for Imperial Airways, and the effect of this glamorous mode of travel on a small Irish port. Even today, airplanes like the Catalina, the Short Empire class, and the majestic Boeing B-314 Clippers speak of a time now long gone.

Click on the link to celebrate the memory of the age, and the life and times of those who lived it.

Click here to listen to the podcast (MP3, 28MB).

Click here to listen to the podcast on iTunes.

Click here to view the transcript of this podcast (PDF, 585K).

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Audio for Podcasting: Hard Disk Recording

When digital audio first appeared, tape-based digital recorders using Digital Audio Tape (DAT) were the only viable system for recording the relatively large amount of data required by a digital audio recording system. This was because tape was less expensive to manufacture than hard drives, and tape was easy to store for later reuse. As hardware became more sophisticated, disk drives started to grow in capacity and performance, to a point where by the mid-1980's digital disk recorders started showing up in professional recording studios.

However, storage limitations and exorbitant costs meant that a 10MB drive could cost over $2000, and could hold only about a minute of audio. This worked great for MIDI and music sequencer applications like Cubase, running on the Atari ST computer (see Figure 1) but was insufficient for recording and editing high-quality voice-over narration.

Figure 1. Start of an audio revolution: Cubase 1.0 for Atari ST
[Click to enlarge]

However, as computers became more powerful, so the hard disk capacity used to store data on a computer grew. Its now common to see disk drives that store 100, 200, or even 500 gigabytes (GB) of data. Storing digital audio on hard disk makes a lot more sense and in fact now the most affordable alternative. Today you can buy a one terabyte hard disk for about $300 that gives you hundreds of hours of stereo, 16-bit recording at a 44.1K sample rate.

Advantages of Hard Disk Recording
There are a variety of reasons why hard disk recorders are more versatile and powerful than their tape-based cousins. Advantages include:

1. Instant access time. The most expensive part of most tape machines is the motors that control the motion of the tape, called the transport. Transports are often very complex mechanical devices with very precise tolerances. Since a tape machine has to physically move tape linearly across the tape heads, and shuttle the tape from beginning to end, a powerful and reliable transport is required. The better the transport, the faster you can get from one portion of the tape to another, which saves time.
   
   A hard disk drive does not have this limitation. Hard drives are now fast enough so that any data stored on a hard disk drive can be accessed in an instant of time. This means that locating any portion of a song can be done almost instantaneously since there is no tape to wind. The elimination of rewind and fast-forward locate time is a huge benefit of hard disk recording. The less time spent winding tape, the more time can be spent getting the best take recorded instead.
   
2. Flexible and powerful editing. In tape-based systems, there are two methods of editing the audio on tape: re-recording over it, or physically cutting the tape. You can record over existing material on a tape deck or record between two tape machines insert new portions of audio or move audio into a new location. The problem with editing with tape this way is that in order to perform the edit you must wipe the original material by recording over it; this is sometimes referred to as "destructive editing". In addition, since you are recording, it takes at least as long as the length of the edit to perform it, that is, inserting a one-minute audio segment will take one minute.
   
   With hard disk based recording, the data that is on the disk can be re-arranged without having to be deleted. This is often called "non-destructive editing". The audio data on disk can be also be manipulated in many different ways. The power that a disk recorder provides over tape recorders in terms of editing is substantial.
   
3. Processing the audio. In addition to editing the digital audio data stored on a hard disk (by cutting, copying and pasting), audio can be processed using software algorithms called digital signal processing or DSP. Using DSP, audio stored on hard disk can be stretched and squeezed, raised and lowered in amplitude, put on its head and turned inside out just by re-arranging the zeros and ones. Additionally, a DSP-based hard disk recorder provides one of the most substantial benefits of digital audio in the first place because audio can be manipulated and processed while remaining in the digital domain. The only practical way to perform DSP operations on digital audio is when it is stored on hard disk. Tape-based systems, with their linear recording processes makes advanced DSP features impractical to implement, regardless of tape format used.

Next time: Authoring your podcast using an audio editor.

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Podcasting for E-Learning: Benefits of Digital Audio

The first principle of digital audio is:

Digital audio is the study of discrete values.

This characteristic is very important: it allows us to manage audio information very efficiently. Using digital techniques, the capability to process information is greatly enhanced.

In a previous post, I discussed a little about the basics of digital audio. Today, I want to talk about how digital audio technology benefits podcasters. What are its advantages over an analog system of recording?

Here are a few specifics:

1. Less noise than an analog recording system.
   In an analog recording system, magnetic particles are oriented by the tape head in a manner that is analogous with the audio signal that is driving the tape head. The tape itself has billions of little magnets on it, and it is physically impossible to orient every single one correctly. These remaining magnetic particles are randomly oriented, which shows up on playback as what is called tape hiss. With a high enough sample rate and resolution, digital audio produces recordings that have significantly less noise than analog.
   
   The noise in an analog recording system is usually expressed as a "signal to noise ratio". The signal to noise ratio tells you how much more signal there is on the tape recorder outputs compared to the noise in a audio signal. For example, a digital audio system using a resolution of 16 bits will often yield a signal to noise ratio of more than -90dB (in EMG’s in-house studio the noise threshold is, for example) for decibel, a unit of measurement in the audio world. -90dB means that the noise floor is 90dB below the signal level.
   
   It would take a very high-end and expensive analog recording system to produce even a signal to noise ratio of -60db. This difference of 30dB is dramatic: the noise floor in the analog recording system will be 1000 times louder than the noise floor in a digital system. The reason for this is quite simple: a digital recording system records only the binary numbers, not analog signals which accumulate noise from the imperfect recording process. Since a digital system only records numbers (zeroes and ones, or bits, to be specific), as long as the bits can be recorded and read by the digital tape or digital disk system, then the only thing that matters is the theoretical 6dB per bit of dynamic range that is determined by the resolution of the digital recording system.
   
2. Ability to make copies without signal loss.
   Another advantage of digital audio over analog is the ability to make as many copies of the original as you want without degrading the signal quality. Every time you duplicate an analog recording, you lose audio quality and add even more noise. Remember that digital audio is just a group of digital samples, made up of zeros and ones that represent the audio.
   
   These numbers can be "copied" to another device or medium in a way that ensures that the result is the same as the original. This means that the copy is a "clone" of the original and sounds the same. This is true for the first copy or the seventy-first. Each time you copy an analog recording, you introduce between 3 and 6dB of noise, which further reduces the signal to noise ratio. Clearly, for pristine back-up want to use multiple copies of material during production, digital has the advantage.
   
3. Better audio quality for a lower cost.
   Digital audio used to be much more expensive than analog. This was because the early digital tape recorders used expensive and precise reel-to-reel mechanisms and early digital technology which was inherently more expensive. As recently as five years ago, the cheapest digital multi-track on the market was over $10,000 - analog reel-to-reel machines could be had for a fraction of that price. Now, digital technology has advanced to the point that this is no longer true.
   
   This is much in part to the advancements made in digital technology due to computers as well as cost reduction of other technologies important to digital recording like video cassette mechanisms and hard disk drives. Since digital audio technology uses similar components as the computer and multimedia industries, digital audio devices can take advantage of the lower cost of components due to their high manufacturing volumes. The result? Today's digital audio multi-tracks not only out-perform analog machines, costs less to manufacture, and is quite easily integrated into a multimedia production environment.

More...

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New E-Learning Curve’s Other Podcast episode release:

Part 7 of Transatlantic: The Flying Boats of Foynes

In Part 7: End of an Era

The War in Europe ended on May 25th, 1945. As normal life re-established itself, times also began to change for Foynes. Larger and more powerful airplanes had been built and operated successfully. A new land-based airport was established at the far side of the river. It was called Shannon International.

In this final episode of Transatlantic: The Flying Boats of Foynes, Chief Operator of Launch Operations Frank Buckley describes the end of the flying boat service in Foynes, Ireland, and the emergence of Shannon airport as the new home for transatlantic aircraft in the Post-War years.

Click here to listen to the podcast (MP3, 8.5MB).

Click here to view the transcript of this podcast (PDF, 24K).

Even though this is an e-learning blog, the observant among you will notice that the podcast isn’t about e-learning. That’s OK – the point of e-learning is to provide training professionals with a means of creating and distributing content that enables people to acquire information, knowledge, skills, and expertise on a diverse range of subjects: as e-learning practitioners, it’s our job to facilitate this process.

Podcasting for E-Learning: Critically Analyzing Podcasts

My previous blog posts on podcasting have focused the human side of podcasting: narration, story-telling, communicating with your audience. I've looked at what you say, and how you say it, dipping liberally into the eighty or so years of accumulated skills and knowledge from radio broadcasting to reinforce my arguments - after all, content is king, and radio is still the place where people talk.

Now, it's time to spend a little time understanding the technical aspects of podcasting. Don't worry if you've never so much as looked at a sound file before. Recording and producing your own content is great fun, and I hope you'll find that there's tremendous satisfaction to be had creating and crafting your own little corner of the internet.

As you begin to hone your podcasting skills, you'll find that you're also taking a remarkable learning journey. It's one that I think will enhance the way to sense and think about the medium of sound. If you are a musician, you'll already know what I mean. Those of you who can play (even if it's only a few chords on the guitar) know that you listen to music in a qualitatively different way to those don't play. The very act of learning an instrument teaches you to become an active listener and a critical analyst of sound. How is that musical piece orchestrated? How are the harmonies arranged, what technique is that soloist using? What melodic elements hold your attention? As well as just enjoying a musical number on its own merits, you can apply a critical ear to the music, and I would suggest appreciate a work in a much more profound way than the casual listener. The same principles apply when you begin to podcast.

Jack Herrington (2005) agrees with this interpretation. In his text Podcasting hacks: tips & tools for blogging out loud, he considers that there are four elements you should critically examine:

Podcast Structure: Analyze content for recurring or format elements used to keep the listener engaged with the podcast, and to motivate the listener to return for future elements. Is the "interesting stuff" (p.51) at the beginning, the middle, the conclusion, or distributed throughout the pod cast presentation.

Technical Elements: Podcast should take advantage of appropriate Web 2.0 and multimedia components to be effective. In some instances, this can mean a voice-over narrating a story very simply. In other contexts, a podcast may take advantage of music, wildtrack, multiple voices, and sound effects.

Content: Try to understand what holds your attention. This is especially vital: according to Herrington, it's what "primarily keeps people coming back" to listen again. The author suggests that

"When something moves you, listen to it over and over to figure out what is keeping you engaged."

(p.52)

Next time: Fundamentals of Digital Audio Editing

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New E-Learning Curve’s Other Podcast episode release:

In Part 6: The Flying Boats at War

During World War II, the civilian airlines of the Allies continued to fly, though perhaps the nature of the passengers had changed. As the US, Britain, and their allies prepared for the invasion of Europe,

In this episode, Chief Operator of Launch Operations Frank Buckley describes working on the flying boats during the War, the hazards that the aircraft encountered, searching for the German battleship Bismarck, and the excitement of the night-time take-offs and landings.

Click here to listen to the podcast (MP3, 11MB).

Click here to view the transcript of this podcast (PDF, 24K).

Even though this is an e-learning blog, the observant among you will notice that the podcast isn’t about e-learning. That’s OK – the point of e-learning is to provide training professionals with a means of creating and distributing content that enables people to acquire information, knowledge, skills, and expertise on a diverse range of subjects: as e-learning practitioners, it’s our job to facilitate this process.

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References:

Herrington, J. D. (2005). Podcasting hacks: tips & tools for blogging out loud. O'Reilly Media, Inc.

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Podcasting for E-Learning: Digital Audio Basics

Really exceptional podcasts transmit a sense of "being there."

Well-designed, planned, narrated and produced audio content has the facility to engage the audience and transport the listener, providing the right cognitive environment for learning or entertainment or whatever goal the podcast seeks to achieve. As the old story goes, “there are better pictures on the radio.” Denis Nowlan, Deputy to the Controller for BBC Radio 4 describes this as

the wonder of radio [and sound] …the conjuring of magical sounds, Prospero-like, out of the silently teeming air. And the sense of joining, instantly, with a vast community of listeners.

(2005)

Of course, this cognitively experienced sense of “being there” is a completely artificial construct, none more so when you consider audio podcasting. The journey the podcaster takes us on is based on nothing in nature; that is, a narrative transmitted as binary data: electronically-mediated zeros and ones.

I will discuss this phenomenon in detail next time, but for now, read on…

Digital audio is actually very similar in concept to motion film, where a rapid series of still photographs make up a “motion picture.” Digital recording reproduces audio signals by taking many still “pictures” – or samples - of an audio waveform and then reconstructing the waveform for playback digitally (see Figure 1).

Figure 1. Digital Sampling of Audio Waveform
[Click to Enlarge]

In film, the number of still images (frames) we move through the projector per second improves the smoothness and quality of picture we see. Similarly, the size of the film's light-sensitive crystals in each frame determines the visual resolution of the image - and we all know movies look better in 70mm as opposed to the 35mm or 16mm film.

In digital audio, an analog signal is typically sampled 44,100 times a second. Each sample is created by taking a "snapshot" of the amplitude (or strength) of an analog audio signal at a particular moment in time. and converting that amplitude into a binary number.

The number of samples contained in each second of audio is called the sample rate. The greater the number of samples per second, the greater the resolution of the audio signal.

Let’s return to the film analogy: the faster the film rate through the camera, the better the ability of the film to pick up motion. For example, if you crank a film camera too slowly, then motion past a camera is not smooth since the frame rate does not capture enough frames in a given amount of time to stop the motion from appearing to jump or jerk - too much action happens in front of the camera "between frames" for the motion to appear natural.

Time for an example: The resolution of an audio CD is 16 bits and the sample rate is 44.1KHz. This means that the audio is sampled 44,100 times a second and a series of 16 zeros and ones is used to define the amplitude of the waveform at each of those 44,100 points.

This resolution – commonly called “CD Quality” and should be your baseline for recording a podcast. When recording voice-over narration, capture all of your audio at 16 bit, 44.1KHz, in mono using the WAV format in Windows, Au format for Unix-based systems (like Linux), and AIFF for Apple Mac.

More...

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References:

Nowlan, D. (2005). Radio: where the pictures are better: Denis Nowlan speaks for the medium which leads you by the ear. [Internet] Available from: http://findarticles.com/p/articles/mi_m0KZH/is_1_19/ai_n15928065/ Accessed 12 August 2009.

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