Introduction

With the increased popularity of portable media players and podcasts, web audio has become another method of creating, disseminating, and consuming information for creativity, learning, and entertainment. We are all familiar with digital music that can be shared and listened to online, but audio supports myriad other forms of expression, like telling stories, augmenting visual presentations, and reporting – all of which could arguably be considered forms of digital storytelling.

Inevitably, when talking about digital audio the conversation turns to issues of copyright and fair use. As a rule of thumb, always ensure you have written permission to use audio resources in your work. There are too many legal rulings against individuals who have “infringed” on copyright, particularly in the music industry, to take the issue lightly. When in doubt search for Creative Commons licensed work or work that has fallen into the public domain. There are a number or resources listed farther down on this page.


Objectives

  • Understand the basics terminology used when creating digital audio
  • Find audio for reuse
  • Record your own audio
  • Use Audacity to edit a multi-track audio recording

Read & Watch

 

 


Lecture

When recording and optimizing audio, just as with images, remember that the amount of space used on disk for the file is directly affected by the quality of the sound. The process of sampling /optimizing audio is a trade off between small file size and the quality of the sound.

Just as with images, audio can be compressed by lossless or lossy algorithms. Lossless compression is commonly used when editing, in master copies of recordings (as well as archival copies), and by audiophiles. Common Lossless formats are FLAC, APE, WV, AIFF, and WAV. Lossy compression is typically what you will encounter on the internet because file sizes tend to be smaller. Common lossy formats include MP3, OGG, AAC, Musepack, and lossy WMA.

There are a handful of common audio file formats used on the web. They include:

  • AU (Audio Format) – not great quality because it uses 8-bit encoding (.au)
  • *WAV (Wave) – Provides good quality, uncompressed files that uses 16-bit encoding. It is native to Windows and commonly produces larger file sizes. (.wav)
  • AIFF (Audio Interchange File Format) – This is a Mac-based format that uses 8 or 16-bit encoding. It produces similar-quality sound to WAV and is an uncompressed format. (.aiff or .aiff)
  • *MP3 – One of the most popular formats for making audio available on the web, it is supported by most popular browsers. The encoding uses lossy compression that provides quality sound through a method called perceptual coding. (.mp3)
  • MIDI (Musical Instrument Digital Interface) – MIDI files can only store instructions for notes, not sound and because of this file sizes are very small. (.mid or .midi)

WAV and MP3 formats are usually your best bet if you want to make audio available on the web. Keep in mind that MP3 will generally compress better than WAV and give you a smaller file.

Streaming audio is served differently than stand-alone audio files and often uses proprietary file formats that require a streaming server to deliver files.

  • .rm (Real Media)
  • .asf (Advanced Streaming format)
  • .asx (Advanced Stream Redirector)
  • .wmv (Windows Media Video)
  • .wma (Windows Media Audio)

Audio Terms

Bit Rate – When creating audio you will find that the lower the bit rate used, the smaller the size of the file will be. Bit rate determines how much space on disk a file will use per second. 128 kbit/s is commonly found online.

Bit Depth (resolution) – Limits the dynamic range of a recording. A depth of 16bit matches audio CDs. More information at http://wiki.audacityteam.org/index.php?title=Bit_Depth

Sampling Rate – the number of times an audio file is sampled, in a given period of time; the highest pitch an audio file can produce is exactly half of the sampling rate, so higher frequencies produce greater range which means higher quality audio. A sample rate of 44.1kHz is used for creating CD audio. More information on sample rate at http://wiki.audacityteam.org/index.php?title=Sample_Rates

More audio terms are defined in the Audacity Glossary here: http://manual.audacityteam.org/index.php?title=Glossary


Acquiring Audio Files

Download:
http://www.freesound.org
http://ccmixter.org
http://wiki.creativecommons.org/Audio
http://www.archive.org/details/audio
http://www.jamendo.com
http://soundcloud.com
Free Music Archive
Netlabels on Archive.org

Create:
http://audacity.sourceforge.net (you will also need to download the LAME encoder to export you recordings to MP3 found here: http://lame.buanzo.com.ar)


Activities

Locate an audio file to work on by visiting one of the download sites listed above. Some sites will require you to create an account before you can download files. Once you find a sample or song you want to work with be sure to note the artist and license (check that you are permitted to use the file) so you can properly credit that artist in your finished work. Download the audio file and open it in Audacity.

Familiarize yourself with the Audacity interface.

There are four toolbars to take note of:

Control Toolbar
Control Toolbar

Edit Toolbar
Edit Toolbar

Mixer Toolbar
Mixer Toolbar

Meter Toolbar
Meter Toolbar

 

Audio Editing Basics with Audacity


Best Practices for Creating Web Audio

If you’re going to record your own audio the following are a few items to keep in mind.

  • Monitor your levels. If your levels are too low the audio will be difficult to hear, but if your levels are set too high you encounter distortion
  • Select a location to that is conducive to recording audio. Eliminate the possibility of accidentally recording background noises like air handlers, traffic, or the neighbor’s dog
  • Edit out vocal stumbles. Also, whenever you’re editing audio use headphones so you can hear more of what is going on in the file(s)
  • If you have vocal tracks, normalize them to even out uneven vocal fluctuation
  • Amplify the tracks as loud as they can go (without introducing distortion). Be sure and double check the gain by playing back the tracks
  • Export your project to MP3. This mixes your tracks into a single file
  • Add information about the file to the ID3 tags

Using Audacity

Review the following resources and become familiar with editing with Audacity:

More Audacity resources can be found here:

You may occasionally encounter an audio format that will not import into Audacity. In the past I have had decent success converting that file into another format using a free online file conversion tool (I use Zamar – http://www.zamzar.com). Typically the process for converting a file this way involves uploading your file, selecting a target file type to be converted to, and waiting for the converted file to be delivered to you. For infrequent conversion this seems to work well. There are also paid online converters and application-based converters that can also perform these tasks for you if you convert a high volume of files.


Placing Audio on a Web Page

We won’t be embedding audio in an HTML page in this class but if you’re interested in learning how W3Schools has a succinct resource that will get you started with a few current strategies for linking audio. HTML 5 will link audio using an <audio> tag, so note that change is coming. If you’re running a browser that supports HTML 5 you can try the code out for yourself. To share your audio file you can upload it to SoundCloud or try linking it to an HTML page and sharing it on your web server.


Sound Story Example:


Looking forward

Before you move on, complete this week’s Assignment 9.