Bandwidth : how many bits to record that sound...

 how many bits :
 * http://en.wikipedia.org/wiki/List_of_device_bandwidths
   * http://en.wikipedia.org/wiki/Binary_prefixes

 which is based on 
 * http://en.wikipedia.org/wiki/Psychoacoustic_model

 Human hearing:
  20Hz ... 20kHz, with resolution ~ 2Hz

 "CD quality" : 
  bandwidth = 2 channels x 16 bits/sample (e.g. 65536:1 dynamic range) x 44.1kHz 
            = 1_411_200 bits/second = 1.4Mbit/s
     Note several sources of common confusion in this unit:
     * 8 bits (b) = 1 bytes (B); both are commonly used for computers
     * k | M | G  decmimal = 10^3 | 10^6 | 10^9 = 1,000 | 1,000,000 | 1,000,000,000 
                   as used by scientists and network bandwidth engineers,
       k | M | G binary = 2^10 | 2^20 | 2^30 = 1,024 | 1,048,576 | 1,073,741,824
                   used for computer memory (megabytes) 
	   international standards say these are ki | Mi | Gi but not in common use.

  
  phone line = DS0 = 64 kbit/s
  modem: 28 kbit/s around here                               dial-up

  T1 = DS1 = 24 phone lines = 1.54 Mbit/s (decimal M)        college to internet
  T3 = DS3 = 44.74 Mbit/sec ('45 Meg')

  802.11b = 11 Mbit/s                                        campus wireless

  ethernet = 10base-X   = 10 Mbit/s   ("fast ethernet")      campus network
          or 100base-X  = 100 Mbit/s
          or 1000base-X = 1 Gbit/s    ("gigabit ethernet")

  USB 1.0  =   1.536 Mbit/s
  Firewire = 400 Mbit/s
  USB 2.0  = 480 Mbit/s

 Quick quiz: 
   * what's the highest frequency if sampling rate is 44kHz?
   * how many phone lines to transfer CD quality sound at same rate it gets played?

 audio compact disk
 * http://www.ee.washington.edu/conselec/CE/kuhn/cdaudio/95x6.htm
 * http://www.ee.washington.edu/conselec/CE/kuhn/cdaudio2/95x7.htm
 * http://en.wikipedia.org/wiki/Audio_CD
   
 from whatis.techtarget.com:
 The CD-ROM, like other CD adaptations, has data encoded in a spiral
 track beginning at the center and ending at the outermost edge of the
 disc. The spiral track holds approximately 650 MB of data. That's
 about 5.5 billion bits. The distance between two rows of pits,
 measured from the center of one track to the center of the next track
 is referred to as track pitch. The track pitch can range from 1.5 to
 1.7 microns, but in most cases is 1.6 microns.

 audio CD has about 74 minutes or about 650 megabytes

 compression :
 * http://en.wikipedia.org/wiki/Audio_compression

 audio codecs and file formats
 * http://en.wikipedia.org/wiki/Codec

 
 "codec" is description of what the bit stream means
 "file format" is how it gets put on a disk (including headers and metadata)

 "lossless"
    .wav (http://en.wikipedia.org/wiki/WAV)
    FLAC (http://en.wikipedia.org/wiki/FLAC)
      compression designed for audio; 
      30-70% compression compared to 20-40% for zip

 "lossy"
     .mp3  (MPEG-1/2 Audio Layer 3) 
      * http://en.wikipedia.org/wiki/Mp3

     .ogg  Ogg Vorbis
     * http://en.wikipedia.org/wiki/Vorbis
  

  mp3 : 
         excellent at 256..384 kbit/s
         very good at 224..256 kbit/s
         good      at 128..192 kbit/s

     wikipedia :

      Many listeners accept the MP3 bitrate of 128 kilobits per second
      (kbit/s) as near enough to CD quality for them; this provides a
      compression ratio of approximately 11:1, although listening
      tests show that with a bit of practice, many listeners can
      reliably distinguish 128 kbit/s MP3s from CD originals. To some
      listeners, 128 kbit/s is unacceptably low quality. Even though
      differences may be perceptible, this is acceptable for some listeners
      in some listening environments, such as a noisy car or train.

      encoders : LAME is an open source MP3 compression application