Types of Digital Audio

Audio is recorded sound. There are many different ways to record sound; after recording sound, there are many different ways of listening to audio. Today, audio almost always means digital audio, or sound that is recorded and played using a computer. Normally, audio is recorded using microphones that are fed into computers, and computers save the audio into electronic files. Then, these files can be burned to a CD or DVD, put on a media player, and listened to nearly anywhere.

Even though sound is the same everywhere, there are different kinds of audio files that are common. These files save, as exactly as possible, everything the computer hears. Because these files save every last detail, these files can be very big files. The two most common types are:

• WAV (Waveform Audio Format), commonly used on PCs
• AIFF (Audio Interchange File Format), commonly used on Macs

There are many other files that try to make audio files smaller by ignoring details that are hard to hear. These files follow patterns, called codecs, which tell the computer which details are ignored so that computers can record and play back these files. These files are often called lossy formats, because the ignored details are “lost” and aren't in the audio. There are three very common lossy formats:

• AAC (Advanced Audio Coding), used in Apple software (like iTunes and QuickTime)
• WMA (Windows Media Audio), used in Microsoft Software (like Windows Media Player)
• MP3 (MPEG-1 Audio Layer 3), for most kinds of software, including Apple and Microsoft

Audio Editing

Audio Editing is using a computer to change the digital audio. Audio editing is done for many reasons: it can cut out the “fuzz” in a recording, or adjust a recording to make it sound clearer. Audio editing can also be used to add and combine different sounds, especially music, to make new sounds and new kinds of music. It is not uncommon to make music without touching a real instrument, using a computer to mix and combine sounds into a new music piece.

Audacity is a powerful, free and open source audio recorder and editor. It provides many features and effects to create and modify sound. In this module, we will begin with making a sound loop in Audacity.

In Windows, open Audacity by either clicking on the icon on the desktop (if it's there), or by going to the Start Menu, selecting “Programs” or “All Programs,” and finding Audacity from that list.

We are presented with Audacity with no open files. The buttons and diagrams at the top are Audacity's toolbars. The large grey area of the screen is where sound will be shown, broken up by tracks. These tracks make up part of the sound, which are played together to make a whole. In most cases, these tracks represent individual instruments.  This way, we can change how each individual instrument sounds, like making the drums a little quieter, while keeping the other instruments the same.