Topic Introduction to Multimedia and the elements of Multimedia

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					Topic 6

Sound
Content

   The importance of sound
   Sampling
   Using Sound for Multimedia
    Applications
   Concept of sound
   Type of audio formats
   Editing
The Importance of Sound

     Attract attention
     Convey an idea
     Elicit an emotion
     Dramatize point
     Sense of realism
 Sampling

In order for a computer to work with audio waves,
they must be converted from analog to digital
form. This is done through a process called
sampling, in which every fraction of a second a
sample of the audio is recorded in digital bits.
        Sampling
    There are two factors that affect the quality of the
    digitized audio.
    1. Sample Rate
   Sample rate is the number of times the sample is taken.
   The three most common sample rates are; 11.025 kHz,
    22.05 kHz, and 44.1 kHz.
   The higher the sample rate, the more samples that are
    taken and, thus, the better the quality of the digitized
    audio.
    2. Sample Size
   Sample size is the amount of information stored about
    the sample.
         Sampling
   Audio can be categorized in two general formats, mono
    and stereo.
   Mono is the reproduction of sound using a single-
    channel.
   Stereo is the reproduction of sound, using two or more
    independent audio channels, through a symmetrical
    configuration of loudspeakers, in such a way as to create
    a pleasant and natural impression of sound heard from
    various directions, as in natural hearing.
          Sampling
The following formula is used to determine the byte size
of a 1 second recording:

   1 second recording at a sample rate of 44.1 kHz and 16
   bits would be 88, 200 bytes (44 100 x 16 / 8). You would
   double this number for a stereo recording. The 44.1 kHz
   16-bit sample is CD quality, whereas the 11.025 kHz 8-
   bit sample would be marginal quality.
Formula :
Duration * Channel * Sample rate * Sample Size
    (s)    (Mono / Stereo)      (Hz)             (Byte)
Using Sound For Multimedia
Applications

  o Background music
  o Sound effects
  o Narration
   Concept of Sound

Analog Audio

A representation of an object that resembles the
original. Analog devices monitor conditions, such as
movement, temperature and sound, and convert
them into analogous electronic or mechanical
patterns. For example, an analog watch represents
the planet's rotation with the rotating hands on the
watch face.
Concept of Sound




       Analog Wave
      Concept of Sound

Analog wave patterns – these wave patterns have two
attributes

   Volume – the height of each peak in the sound wave
   Frequency – (sometimes referred to as pitch) the
    distance between the peaks. The greater the
    distance, the lower the sound.
         Concept of Sound

Digital Audio
  Refers to the reproduction and transmission of sound
  stored in a digital format. This includes CDs as well as any
  sound files stored on a computer.
  Sound waves that have been digitized and stored in the
  computer. Common digital audio formats are music CDs,
  MP3, WAV and AIFF. Many CD players also play MP3
  files; however, software-based players play the largest
  variety of audio formats. Although also in digital form, MIDI
  music is generally not considered digital audio. MIDI files
  contain a coded version of the musical score, not the
  actual sound.
        Concept of Sound
MIDI

 (Musical Instrument Digital Interface) A standard
 protocol for the interchange of musical information
 between musical instruments, synthesizers and
 computers. MIDI was developed to allow the keyboard of
 one synthesizer to play notes generated by another. It
 defines codes for musical notes as well as button, dial and
 pedal adjustments, and MIDI control messages can
 orchestrate a series of synthesizers, each playing a part of
 the musical score. MIDI Version 1.0 was introduced in
 1983.
Concept of Sound
Types of Audio Format


    Wave files
    Midi files
    MP3
       Editing
These are the basic sound editing operations that most
multimedia producers need.
 Trimming
 Splicing and Assembly
 Volume Adjustments
 Format Conversion
 Resampling or Downsampling
 Fade-ins and Fade-Outs
 Equalization
 Time Stretching
 Digital Signal Processing (DSP)
 Reversing Sounds

				
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