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Updated:  6/6/2022
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DIGITAL AUDIO

DIGITAL AUDIO is a method of representing sound as numerical values. In contrast, analog systems like, magnetic tape, or vinyl records, rely on physical methods to reproduce the sound.

AUDACITY VOCABULARY TERMS 1.docx
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What is MP3?

MP3s (which stands for Moving Picture Experts Group, Layer 3) are digital audio files that are compressed to about 1/10 the size of a CD recording. Your computer compresses files by scanning them for repeating patterns of digits. It then replaces these patterns with smaller codes that take up less space. So, you can compress a CD song that has 50 megabytes of data into an MP3 that has only 4 or 5 megabytes (1 megabyte = 1,000,000 bytes; 1 byte = the size of 1 computer character, like the letter "a"). As a result, MP3s are compact enough to send over the Internet with little difference in sound quality.
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What is an MP3 file and how does it differ from WAV and AIFF files?

MP3 (MPEG II, layer 3) is a popular format for storing music and other audio. A typical MP3 file is one tenth the size of the original WAV or AIFF file, but it sounds very similar. MP3 encoders make use of psychoacoustic models to, in effect, "throw away" the parts of the sound that are very hard to hear, while leaving the loudest and most important parts alone.

Unfortunately, no MP3 encoder is perfect, and so an MP3 file will never sound quite as good as the original. Still, most people find that the quality of an MP3 file is virtually indistinguishable from a CD when played on headphones or on small computer speakers, which is why the format is so popular


A Brief History. . . . 
  • The German company Fraunhofer-Gesellshaft developed MP3 technology and now licenses the patent rights to the audio compression technology - United States Patent 5,579,430 for a "digital encoding process". The inventors named on the MP3 patent are Bernhard Grill, Karl-Heinz Brandenburg, Thomas Sporer, Bernd Kurten, and Ernst Eberlein.
  • In 1987, the prestigious Fraunhofer Institut Integrierte Schaltungen research center (part of Fraunhofer Gesellschaft) began researching high quality, low bit-rate audio coding, a project named EUREKA project EU147, Digital Audio Broadcasting (DAB). 
  • Two names are mentioned most frequently in connection with the development of MP3. The Fraunhofer Institut was helped with their audio coding by Dieter Seitzer, a professor at the University of Erlangen. Dieter Seitzer had been working on the quality transfer of music over a standard phone line. The Fraunhofer research was led by Karlheinz Brandenburg often called the "father of MP3". Karlheinz Brandenburg was a specialist in mathematics and electronics and had been researching methods of compressing music since 1977. In an interview with Intel, Karlheinz Brandenburg described how MP3 took several years to fully develop and almost failed. Brandenburg stated "In 1991, the project almost died. During modification tests, the encoding simply did not want to work properly. Two days before submission of the first version of the MP3 codec, we found the compiler error."
  • In 1997, 18-year-old Justin Frankel of Sedona, Arizona, created the first popular MP3 player. Called Winamp, the player is a computer program that converts MP3 audio (sound) files from computer numbers or digits into sound waves you hear through your computer's speakers. Today, listening to MP3s is so widespread, the most common word used on all Internet search engines (sites that find Web pages to match words you type in) is "MP3." And Frankel, a mere 20 years old, is a multimillionaire!
                                                                                               The History of MP3

File Formats

1.  Audacity Project format (AUP)
Audacity projects are stored in an AUP file, which is a format that has been highly optimized for Audacity so that it can open and save projects extremely quickly. In order to achieve this speed, Audacity breaks larger audio files into several smaller pieces and stores these pieces in a directory with a similar name as the project. For example, if you name a project "chanson", then Audacity will create a project file called chanson.aup which stores the general information about your project, and it will store your audio in several files inside a directory called chanson_data. The Audacity Project format is not compatible with any other audio programs, so when you are finished working on a project and you want to be able to edit the audio in another program, select Export.

2.  WAV (Windows Wave format)
This is the default uncompressed audio format on Windows, and is supported on almost all computer systems. It can also be lightly compressed (about 4:1) using the ADPCM codec, but this is less widely supported on non-windows platforms. Audacity can read and write this format, including ADPCM on all platforms.

3.  AIFF (Audio Interchange File Format)
This is the default uncompressed audio format on the Macintosh, and it is supported by most computer systems, but it is not quite as common as the WAV format. Audacity can read and write this format.


4.  MP3 (MPEG I, layer 3)
This is a compressed audio format that is a very popular way to store music. It can compress audio by a factor of 10:1 with little degradation in quality. Audacity can both import and export this format. For more information on how to export MP3 files from within Audacity, see Exporting MP3 Files.

5.  Ogg Vorbis
This is a new compressed audio format that was designed to be a free alternative to MP3 files. Ogg Vorbis files are not as common, but they are about the same size as MP3 with better quality and no patent restrictions. Audacity can import and export this format.

6.  AAC (Advanced Audio Coding)
AAC is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates. 

AAC is also the default or standard audio format for: Apple's iPhone, iPod, iPad, Nintendo DSi, iTunes, DivX Plus Web Player, Sony's PlayStation 3 and is supported by Sony's PlayStation Portable, latest generation of Sony Walkman, phones from Sony Ericsson, the latest S40 and S60 models from Nokia, Android based phones, Nintendo's Wii (with the Photo Channel 1.1 update installed for Wii consoles purchased before late 2007), and the MPEG-4 video standard.


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