Page 37 - DCAP303_MULTIMEDIA_SYSTEMS

Unit 3: Sound

formula for determining the size of the digital audio notes
Monophonic = Sampling rate * duration of recording in seconds * (bit resolution / 8) * 1
stereo = Sampling rate * duration of recording in seconds * (bit resolution / 8) * 2

• The sampling rate is how often the samples are taken.
• The sample size is the amount of information stored. This is called as bit resolution.

• The number of channels is 2 for stereo and 1 for monophonic.
• The time span of the recording is measured in seconds.
3.2.2 editing Digital recordings

Once a recording has been made, it will almost certainly need to be edited. The basic sound
editing operations that most multimedia procedures needed are described in the paragraphs
that follow:
1. Multiple tasks: Able to edit and combine multiple tracks and then merge the tracks and
export them in a final mix to a single audio file.
2. trimming: Removing dead air or blank space from the front of a recording and an
unnecessary extra time off the end is your first sound editing task.
3. splicing and assembly: Using the same tools mentioned for trimming, you will probably
want to remove the extraneous noises that inevitably creep into recording.
4. volume adjustments: If you are trying to assemble ten different recordings into a single
track there is a little chance that all the segments have the same volume.

5. format Conversion: In some cases your digital audio editing software might read a format
different from that read by your presentation or authoring program.

6. resampling or Downsampling: If you have recorded and edited your sounds at 16 bit
sampling rates but are using lower rates you must resample or downsample the file.
7. equalization: Some programs offer digital equalization capabilities that allow you to modify
a recording frequency content so that it sounds brighter or darker.
8. Digital signal processing: Some programs allow you to process the signal with reverberation,
multitap delay, and other special effects using DSP routines.
9. reversing sounds: Another simple manipulation is to reverse all or a portion of a
digital audio recording. Sounds can produce a surreal, other wordly effect when played
backward.

10. time stretching: Advanced programs let you alter the length of a sound file without
changing its pitch. This feature can be very useful but watch out because most time stretching
algorithms will severely degrade the audio quality.

3.3 the MiDi audio

The Musical Instrument Digital Interface (MIDI) is a communication standard developed for
electronic musical instruments and computers.
Using MIDI, a musician can easily create and edit digital music tracks. The MIDI system records
the notes played, the length of the notes, the dynamics (volume alterations), the tempo, the
instrument being played, and hundreds of other parameters, called control changes.

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