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Use
iTunes to encode one of the songs you
have ripped from a commercial CD (the shorter, the better!) into
the following formats:
Format |
File_Name |
.WAV
44.1 kHz
16 bit (64kbps/channel)
stereo
|
standard.wav |
.WAV
44.100 kHz
16 bit
mono |
standard_mono.wav |
.WAV
11.025 kHz
16 bit
stereo |
low_sample_rate.wav |
.WAV
44.100 kHz
8 bit
stereo
|
low_bit_rate.wav |
.AIFF
44.100 kHz
16 bit
stereo
|
standard.aiff |
.AIFF
make the file size small,
yet
sound acceptable
|
acceptable.aiff |
AAC
44.100 kHz
128 kbps
stereo
|
standard.m4a |
AAC
make the file size small,
yet sound
acceptable |
acceptable.m4a |
.MP3
44.1 kHz
128 mbps
stereo
|
standard.mp3 |
.MP3
make the file size small,
yet sound
acceptable |
acceptable.mp3 |
Save
your files in a folder called audio_formats on your disk. Submit
the folder on a data CD.
Bit Depth
Also
known as Sampling Resolution, Bit Depth, Bit Resolution, or Bit
Rate.
When a snapshot or sample of a sound is taken, the
analog-to-digital converter produces a series of binary numbers
(bits) to describe the sample. The sampling resolution describes
how many bits - as in “0s” and “1s” - are
available to describe a digital recording.
In practice, the bit
resolution defines the dynamic range of a sound . The dynamic range
of a sound represents the difference
between the softest sound present in a recording and the loudest
sound. An 8-bit digitizer has a dynamic range of 96dB. By comparison,
the dynamic range of the human ear is approximately from silence
to 120dB.
Sample
rate describes how frequently (or the amount of time between
sample
intervals) an analog audio signal is “sampled” or
analyzed by the analogue-todigital converter as it is recorded
and converted to a digital format. For example, the standard sample
rate for Compact Discs is 44.1 kHz. Which means 44,100 (or 44.1kHz)
samples (or ‘snapshots’) are taken each second to convert
the sound into a digital format.
In practice, the sample rate defines
the frequency range of a digital recording. Sample rate directly
affects audio fidelity in terms
of upper frequency response: the higher the sample rate, the higher
the available frequency response. A fundamental principle of sampling
states that to accurately capture a sound, the sample rate must
be at least twice the highest frequency in the sound. Higher sampling
rates yield better sound fidelity and larger sound files.
Common
Sample Rates
96.000kHz
- This is the standard sample rate for Digital Video Disc (DVD)
audio, and is often used by sound editors working
in
audio postproduction for DVD. This rate results in an upper frequency
response of 48kHz — well above the range of human hearing.
48.000kHz
- This is one of two standard sample rates for digital audio tape
(DAT) recorders, and is often used by sound editors
working in audio post-production for video or film. This rate results
in an upper frequency response of 24kHz - well above the range
of human hearing.
44.100kHz
- This is the standard sample rate for Compact Discs, digital
audio
tape (DAT) recorders, and high-fidelity
audio applications
on Macintosh and PCcompatible computers with 16- bit playback capability.
It is sometimes called “ forty-four one” (as in 44.1kHz).
Most sound engineers working in music production – or anything
that may be distributed on a CD — work at this rate. This
rate results in an upper frequency response of 22,050Hz — above
most people’s hearing range.
22.050kHz & 11.025kHz - These
sample rates are sometimes used for lowerfidelity audio playback
on Macintosh and PC-compatible
computers. Many games, web-sites and other multimedia productions
utilize 22.050kHz (or lower) 8-bit audio, since it uses half the
disc space of CD quality audio. The 22.050kHz sample rate results
in an upper frequency response of 12.025kHz; this may sound “muffled,” since
most people can hear considerably higher frequencies than 12.025kHz.
Source: Darren Fisher
Note: 1 kilobit = 1,024 bits. Go figure!
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