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MP3 & Digital Audio Guide
Listening to audio from the internet is as simple as
downloading a sound clip and opening it up with an audio
player. A player is an application that lets you listen to
digital sound files with many of them supporting streaming
audio or video as well. There are several sound formats and
a variety of media players available on the web. Thankfully,
there are just a handful of popular formats and players to
choose from.
Audio Formats
Audio files can be either uncompressed or compressed. Most
of the early audio formats were uncompressed which means
that sound files are bigger and take longer to download.
Common uncompressed audio formats include WAV, the native
audio format for Windows, and AIFF (Audio Interchange File
Format), the native format for Macs. Sound files like any
other file type can be recognized by their extensions like
.wav or .mid.
With compression you can cram more sound into a smaller file
which makes it faster to download. MPEG (Motion Picture
Experts Group) is a type of audio and video compression with
several standards. MP3 is a popular file format or codec
(coder/decoder) that compresses a file to about 10% of its
original size.
MP3 is short for MPEG-1 Audio Layer 3. The higher the audio
layer, the more complex the encoding software which leads to
better sound at higher compression. So a highly compressed
file will sound better using Layer 3 encoding than using
Layer 1 encoding. MPEG encoding compresses a file by
stripping out all the irrelevant sounds that our brains
would filter out anyway. Perception research has determined
the general range of human hearing, and sounds beyond that
range (like frequencies only dogs or elephants can hear) can
be discarded with little impact on sound quality.
MP3s can be encoded at varying bit rates (the number of KB
per second). The higher the bit rate, the better the sound
quality. But the trade-off is a larger file. You can encode
MP3s at bit rates from 8 kbps to over 1000 kbps. The usual
standard is 128 kbps which provides CD like playback. At
this rate, about a minute of music is 1 MB in size.
Another common type of audio file is MIDI (Musical
Instrument Digital Interface). Technically it's not a
digital audio format because a MIDI file doesn't actually
contain a sound recording. A file or sequence contains a set
of instructions for how a sound should be played back by a
computer's sound card or a MIDI instrument like a keyboard.
Think of MIDI like digital sheet music that your computer
can read and play.
A MIDI sequence has to be created on a MIDI device which
means that MIDIs are instrumental only though some
sequencing programs can incorporate voice and sound effects.
Playback must also be through a MIDI device so the sound
quality of a file is dependent on the quality of your sound
card or synthesizer. The advantages of MIDI are small files
and easy sound editing. Sequencing programs let you edit
musical notes much like you edit words with a word
processor.
There's another audio format known as MOD (short for
modules) which combines aspects of MIDI and WAV. A MOD file
contains a sequence, the digital sheet music of MIDI, but in
addition there are WAV samples of instruments playing
various notes. Since a MOD contains all the samples
necessary to play a song MOD files sound the same regardless
of your sound card.
Plug-ins and players for MOD and MIDI files are freely
available online for a variety of platforms. What makes MOD
and MIDI music appealing is that much of it is original
composition. So anyone can be a digital composer with
practice and the proper software.
Streaming Audio
Instead of waiting for an entire sound file to download
before you can play it; streaming lets you begin playing a
file while it is still downloading. This alternative method
of delivery is useful if you want to listen to a large file
like a concert. With streaming audio, data from a web server
is transferred as a continuous stream so you're downloading
and listening at the same time. One popular application of
streaming audio is internet radio.
Common streaming audio formats are Real Network’s RealAudio,
Apple's QuickTime and Windows Media Player. Some MP3 players
like Win Amp support streaming MP3 as well.
Sound System
Regardless of the audio file format, the quality of your
computer's sound system plays a large part in sound quality.
MP3s can provide near CD quality playback, but relying on
the average PC's built-in speakers means any audio file will
sound tinny and muffled. A serious audiophile will have a
set of external speakers, a 3D sound card and a subwoofer.
It's also possible to connect your PC to a conventional
stereo system with the right cables. A device from Sonic box
can achieve the same thing wirelessly. One part of the
device attaches to your PC and transmits an audio signal on
an unused FM frequency which can then be picked up by the
tuner in your stereo.
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