Audacity

1- What is a sound?
Sounds are pressure waves of air. If there wasn't any air, we wouldn't be able to hear sounds. There's
no sound in space.
2- What is the speed of sound?
340 meters per second
3- What is faster, the speed of light or the speed of sound?
The speed of light
4- How do you record a sound?
A microphone consists of a small membrane that is free to vibrate, along with a mechanism that
translates movements of the membrane into electrical signals. (The exact electrical mechanism varies
depending on the type of microphone.) So acoustical waves are translated into electrical waves by
the microphone. Typically, higher pressure corresponds to higher voltage, and vice versa.
5- What is the difference between digital and analog sound?
Recording onto a tape is an example of analog recording. Audacity deals with digital recordings −
recordings that have been sampled so that they can be used by a digital computer, like the one you're
using now.
6- Write 3 advantages of digital sound over analog sound?
Digital recording has a lot of benefits over analog recording. Digital files can be copied as many times you want, with no quality loss;and they can be burned to an audio CD or shared via the Internet.
7- What are the factors that determine the quality of digital sound?
There are two factors that determine the
quality of a digital recording:
Sample rate: The rate at which the samples are captured or played back, measured in Hertz
(Hz), or samples per second. An audio CD has a sample rate of 44,100 Hz, often written as
44 KHz for short. This is also the default sample rate that Audacity uses, because audio CDs
are so prevalent.
·
Sample format or sample size: Essentially this is the number of digits in the digital
representation of each sample. Think of the sample rate as the horizontal precision of the
digital waveform, and the sample format as the vertical precision. An audio CD has a
precision of 16 bits, which corresponds to about 5 decimal digits.
8- What audio file formats does Audacity support?
MP3 (MPEG I, layer 3), Ogg Vorbis, and WMA (Windows Media
Audio). Audacity supports MP3 and Ogg Vorbis, but not the proprietary WMA format or the
MPEG4 format (AAC) used by Apple's iTunes
9- Write the difference between PCM audio files and Compressed ones?
PCM stands for Pulse Code Modulation. This is just a fancy name for the technique described
above, where each number in the digital audio file represents exactly one sample in the
waveform. Common examples of PCM files are WAV files, AIFF files, and
Sound Designer II files. Audacity supports WAV, AIFF, and many other PCM files.
·
The other type is compressed files. Earlier formats used logarithmic encodings to squeeze
more dynamic range out of fewer bits for each sample, like the u−law or a−law encoding in
the Sun AU format. Modern compressed audio files use sophisticated psychoacoustics
10- Write examples of each one of them.

http://dl.dropbox.com/u/6991882/audacity-manual-1.2.pdf

http://audacity.sourceforge.net/?lang=es