Digital Audio

Digital Audio Digital audio uses digital signals for sound reproduction. This includes analogue-todigital conversion, digital-to-analogue conversion, storage, and transmission. Digital audio has emerged because of its usefulness in the recording, manipulation, massproduction and distribution of sound. Modern distribution of music across the internet through on-line stores depends on digital recording and digital compression algorithms. Distribution of audio as data files rather than as physical objects has significantly reduced costs of distribution.

Tools Flash-based Players

These are solid state devices that hold digital audio files on internal or external media, such as memory cards. Due to technological limitations, these are relatively low-storage devices, commercially ranging from 128MB to 8GB, such as the second generation iPod nano, the SanDisk Sansa series of players, and the iriver clix, which can often be extended with additional memory. As they are solid state and do not have moving parts, they are very resilient. In effect, they do not suffer limitations that owners of Hard Drive-based players face, such as fears of dropping their player or fragmentation. Such players are commonly integrated into USB keydrives.

Hard Drive-based Players or Digital Jukeboxes

Devices that read digital audio files from a hard drive. These players have higher capacities, ranging from 1.5GB to 160GB, depending on the hard drive technology. At typical encoding rates, this means that thousands of songs — perhaps an entire music collection — can be stored on one player. Because of the storage capacity, devices that also display video and pictures are often hard-drive based.

MP3 CD Players

Devices that can play audio files from a CD-ROM in addition to audio CDs. It uses a lossy compression algorithm that is designed to greatly reduce the amount of data required to represent the audio recording, yet still sound like a faithful reproduction of the original uncompressed audio to most listeners.

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Recorders Editing

Audio editing was a new technology that developed in the middle part of the 20th century with the advent of magnetic tape recording. Originally, editing was done on reel-to-reel tape machines and edits were made with straight razors and special tape to connect pieces of tape that had been cut. Audio editors would listen to recorded tapes at low volumes, and then located specific sounds using a process called scrubbing, which is the slow rocking back and forth of the tape reels across the playback heads of the tape deck. With the development of microcomputer technology, Sound Recordists were able to digitize their recordings and edit them as files on a computer's hard disk. The computer programs responsible for this task are known as digital audio editors. The earliest program to become widely used in this application was a wave editor called Sound Designer in the late 1980s and early 1990s. Sound Designer was created by a company called Digidesign who achieved early industry dominance. In recent years, however, that dominance has been challenged by a number of companies attempting to grab a portion of Digidesign's market share. In recent years, with the growing popularity of GNU/Linux, a number of Open Source software projects have sprung up in order to develop an open source audio editing

program. This movement has been bolstered recently by the development of ALSA, and the Linux low latency kernel patch, which allow the GNU/Linux Operating System to achieve audio processing performance equal to that of commercial operating systems. The multi-platform package Audacity is currently the most fullyfeatured free software audio editor.

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Production

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Optical Disk

In computing, sound reproduction, and video, an optical disc is a flat, circular, usually polycarbonate disc whereon data is stored in the form of pits (or bumps) within a flat surface, usually along a single spiral groove that covers the entire recorded surface of the disc. This data is generally accessed when a special material on the disc (often aluminium) is illuminated with a laser diode. The pits distort the reflected laser light. Most optical discs, with the exception of a few such as black CDROMs designed for the original Sony PlayStation, have a characteristic prismatic or iridescent appearance created by the grooves in the reflective layer. -

Internet

With the Internet’s community increases, a lot of people use it to transfer, record and edit their audio -

Broadband

Broadband in telecommunications is a term which refers to a signalling method which includes or handles a relatively wide range of frequencies which may be divided into channels or frequency bins. Broadband is always a relative term, understood according to its context. The wider the bandwidth, greater is the information carrying capacity. In radio, for example, a very narrow-band signal will carry Morse code; a broader band will carry speech; a still broader band is required to carry music without losing the high audio frequencies required for realistic sound reproduction. A television antenna described as "normal" may be capable of receiving a certain range of channels; one described as "broadband" will receive more channels. In data communications a modem will transmit a bandwidth of 64 kilobits per seconds (kbit/s) over a telephone line; over the same telephone line a bandwidth of several megabits per second can be handled by ADSL, which is described as broadband (relative to a modem over a telephone line, although much less than can be achieved over a fibre optic circuit, for example). -

Flash Memory

Flash memory is non-volatile computer memory that can be electrically erased and reprogrammed. It is a technology that is primarily used in memory cards, USB flash

drives (thumb drives, handy drive, memory stick, flash stick, jump drive), which are used for general storage and transfer of data between computers and other digital products. It is a specific type of EEPROM that is erased and programmed in large blocks; in early flash the entire chip had to be erased at once. Flash memory costs far less than byte-programmable EEPROM and therefore has become the dominant technology wherever a significant amount of non-volatile, solid-state storage is needed. Examples of applications include PDAs and laptop computers, digital audio players, digital cameras and mobile phones. It has also gained some popularity in the game console market, where it is often used instead of EEPROMs or battery-powered static RAM (SRAM) for game save data. -

File Types

There are a handful of audio file types you should be familiar with if you are planning to copy music off the Internet or even copy a CD. If you aren't sure what file types you are working with, you can distinguish any file type on your computer by the extension in the file name. The extension is the set of letters that follows the dot, as is in: seashore.wav. •

Waveform Audio (.wav) Waveform Audio (.wav) is a common file format. Created by Microsoft and IBM, WAV was one of the first audio file types developed for the PC. WAV files are defined as lossless, meaning that files are large and complete; nothing has been lost. Professionally recorded CDs are also a lossless audio source. In contrast, the three audio formats listed below are lossy-redundant and nonauditory data is removed to allow for more compact storage; in essence, some data has been lost. This process of removing data to shrink the file size is called compression. The three file formats below must begin with a lossless format-such as a storebought CD or a computer WAV file-then compress it. Most lossy formats boast little or no detectable change in sound quality. But because each compressing format selects the deleteable data differently, converting one compressed file into another lossy format will sometimes result in lower quality audio. Again, always start with a CD or WAV file, then compress.

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MPEG-1 Audio Layer 3 (.mp3) MPEG-1 Audio Layer 3 (.mp3) is a common, compressed WAV file. MPEG-1 files are about one-twelfth the size of WAV files. This is why MP3 players can accommodate hundreds of songs on a tiny chunk of storage space.

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Windows Media Audio (.wma) Windows Media Audio (.wma) was developed to compete with the MP3 format for Windows Media Player. Microsoft claims that the WMA files are compressed three times more than MP3s yet retain their original sound quality.

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Ogg Vorbis (.ogg) Ogg Vorbis (.ogg) is another compressed source code similar to MP3, but like WMA, more compressed. Ogg Vorbis is also open source (free to all, unlicensed, no strings attached). While MP3 compresses data at a constant bit rate, Ogg uses a variable bit rate. To illustrate-if you are copying chunks of silence into MP3 format, the compression bit rate stays the same as if you were compressing the sound of an entire orchestra. But if you are copying chunks of silence into Ogg, your compression rate will drop to nothing. The rate varies with the need.

Other Audio File Types •

Musical Instrument Digital Interface (.midi) Musical Instrument Digital Interface (.midi) is commonly used for computer keyboards and other computer-based musical tools. MIDI files contain musical notes, rhythm notation and other information often needed by a composer.

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Audio Interchange File (.aif, .aifc or .aiff.) Audio Interchange File (.aif, .aifc or .aiff.) was developed for the Macintosh computer to store audio files.

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Sun Audio (.au) Sun Audio (.au) or Audio/Basic was developed by Sun Microsystems for use on UNIX systems.

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Emblaze Audio (.ea) Emblaze Audio (.ea) was created by Geo and offers compression similar to MP3 formats, but its purpose is to be played with a JAVA applet-a miniature Internet program. Online greeting cards often use JAVA applet programs for motion and .ea sound files to play music.

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Computers

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Usage

As digital audio players have spread, new uses have been found for them. This includes podcasting, in which radio-like programs, or even TV-like video feeds, are automatically downloaded into the device to be played at the owner's convenience. Future A digital audio player (DAP) is a device that stores, organizes and plays audio files. It is more commonly referred to as an MP3 player because of the MP3 format's ubiquity, but DAPs often play many additional file formats. Some formats are proprietary, such as Windows Media Audio (WMA), and to a degree, Advance Audio Coding (AAC) and MP3. Some of these formats also may incorporate restrictive DRM technology, such as Janus and FairPlay, which are often part of certain paid download sites. Other formats are completely patent-free or otherwise open, such as Ogg Vorbis, FLAC, Speex (all part of the Ogg open multimedia project), and Module file formats.