Click above to get retro games delivered to your door ever month!

  Sounds are simply regular pulses or vibrations in air pressure. Sound is
  produced when air particles are set into motion by a vibrating source.
  When the vibrating source pushes out, it compresses the air particles
  around it. As it pulls in, the pressure release pulls the particles apart.
  A vibration composed of both the pressing and the pulling actions causes
  air particles to bump into each other. This motion begins a chain reaction
  that carries the vibration through the air away from the original source.
  Such a motion is called a sound wave.

  The speaker in the IBM PCs and PS/2s is made to vibrate by the electrical
  impulses sent to it by the computer. Because computers normally deal with
  binary numbers, the voltages they produce are either high or low. Every
  transition from one voltage state to another either pushes the speaker
  cone out or relaxes it. A sound is produced when the voltage to the
  speaker goes from low to high to low again, causing the speaker to move
  out and then in. This single vibration, consisting of a pulse out and a
  pulse in, is called a cycle. Through the speaker, a single cycle of sound
  is heard as a click. A continuous sound is produced when a continuous
  stream of pulses is sent to the speaker. As the pulse rate increases, so
  does the pitch of the tone. For example, if you pulse the speaker in and
  out 261.63 times a second (that is, at a rate of 261.63 hertz, or cycles
  per second), you hear the musical note known as middle C. Figure 7-2
  lists the frequencies required to generate other musical notes.


  Note    Frequency       Note   Frequency       Note    Frequency       Note   Frequency
  ----------------------------------------------------------------------------------------------
  C0      16.35           C2     65.41           C4      261.63          C6     1046.50
  C#0     17.32           C#2    69.30           C#4     277.18          C#6    1108.73
  D0      18.35           D2     73.42           D4      293.66          D6     1174.66
  D#0     19.45           D#2    77.78           D#4     311.13          D#6    1244.51
  E0      20.60           E2     82.41           E4      329.63          E6     1328.51
  F0      21.83           F2     87.31           F4      349.23          F6     1396.91
  F#0     23.12           F#2    92.50           F#4     369.99          F#6    1479.98
  G0      24.50           G2     98.00           G4      392.00          G6     1567.98
  G#0     25.96           G#2    103.83          G#4     415.30          G#6    1661.22
  A0      27.50           A2     110.00          A4      440.00          A6     1760.00
  A#0     29.14           A#2    116.54          A#4     466.16          A#6    1864.66
  B0      30.87           B2     123.47          B4      493.88          B6     1975.53
  C1      32.70           C3     130.81          C5      523.25          C7     2093.00
  C#1     34.65           C#3    138.59          C#5     554.37          C#7    2217.46
  D1      36.71           D3     146.83          D5      587.33          D7     2349.32
  D#1     38.89           D#3    155.56          D#5     622.25          D#7    2489.02
  E1      41.20           E3     164.81          E5      659.26          E7     2637.02
  F1      43.65           F3     174.61          F5      698.46          F7     2793.83
  F#1     46.25           F#3    185.00          F#5     739.99          F#7    2959.96
  G1      49.00           G3     196.00          G5      783.99          G7     3135.96
  G#1     51.91           G#3    207.65          G#5     830.61          G#7    3322.44
  A1      55.00           A3     220.00          A5      880.00          A7     3520.00
  A#1     58.27           A#3    233.08          A#5     932.33          A#7    3729.31
  B1      61.74           B3     246.94          B5      987.77          B7     3951.07
                                                                         C8     4186.01
  ----------------------------------------------------------------------------------------------


  Note: Equal Tempered Chromatic Scale; A4 = 440
        American Standard pitch--adopted by the American Standards
        Association in 1936

  Figure 7-2.  Eight octaves of musical note frequencies.

  The average person can hear sounds ranging from roughly 20 to 20,000
  hertz. The IBM PC can generate sounds through its speaker at frequencies
  that could theoretically range from about 18 to more than a million hertz,
  far beyond the range of human hearing. To give this frequency range some
  perspective, compare it to an average human voice, which has a range of
  only 125 to 1000 hertz.

  The speaker that comes with the standard IBM personal computers has no
  volume control and is not really intended for accurate sound reproduction.
  As a result, different frequencies will produce different effects; some
  may sound louder than others and some may have a more accurate pitch. This
  variation is a by-product of the speaker design and is not something you
  can control.