1. Audio

2. Introduction
• This is a necessary element in a multimedia
product.
• In general, the audio associated with hearing
sense or the noise produced briefly known as
the audio.
• Audio is able to influence the emotions and
thoughts of human and be able to attract users.
• They provide a clear picture of a difficult
concept rather than using text or graphics
alone.

3. Introduction (Cont.)
• As an example, the arrangement of words that
form a text to reflect the atmosphere of war.
Through the text, the individual can imagine things
happening, but with the help of audio, individuals
will have better understanding and improve the
emotional involvement to stay in the conflicts in a
clear and focused.
Audio

4. Concept of Audio and Audio Wave
• Basically, when we listen, we have been feeling
the changes in air pressure around us.
• This change is received by the eardrum and then
the impulses are sent and interpreted as a signal
of sound by the brain.
• When no sound waves present, the air pressure is
constant.
• When sound waves reach the eardrum, the air
pressure will change that either high or low rates.

5. Types of Audio File & Compression
File
• Audio files can be divided into two types, analogue
audio and digital audio.
• Original sound can be heard through our ears like
drums, birds twittered, singing live and others are
examples of analogue audio.
• It is a continuous flow of sound waves.

6. Types of Audio File & Compression
File
(Cont.)
• The following is an analogue waveform and digital
waveform.
Analogue Waveform
Digital Waveform

7. Types of Audio File & Compression
File
(Cont.)
• Digital audio file is a digital audio file that has been
translated (convert) in a digital form.
• The aim is to enable computers to understand the
wave that is converted into the form of numbers or
binary (0 and 1).
• This process is called digitization of audio or audio
sampling.
• In the context of this module, the notes basically
cover more on digital audio.

8. Audio Compression
• Audio compression is one way to reduce the
size of audio files.
• There are two types of compression can be
used:
1. Lossless Compression
2. Lossy Compression

9. Audio Compression (Cont.)
Lossless Compression
• This compression can compress the files without
reducing the quality drop compared to lossy
compression.
• Each repetition of the information will use the
concept of representation and not have to repeat
the full details again and again.

10. Audio Compression (Cont.)
Lossy Compression
• This compression causes data quality after
compression to be relatively low compared to
Lossless compression.
• This is because some of the data or information in
the file continues to be ignored or discarded.
• the results can still be accepted by human hearing.

11. Factors Affecting the Quality Audio
1.0 Sample Rate
• It refers to the number of samples of a sound that
are taken per second.
• The higher the sample rate and more information
on the samples taken, the higher quality digital
audio.
• Sample rate is measured in Hertz (Hz).
• Standard sampling rates typically used for an
audio recording is 11,025 kHz, 22.05 kHz and
44.1 kHz.

12. Factors Affecting the Quality Audio
(Cont.)
2.0 Sample Size
• It refers to the amount of information stored in a
sample OR the number of bits used to store
information of the audio.
• Two types of sample size used is 8 bits or 16 bits.
• Audio recorded by using a sample size of 16 bits
has better quality compared to 8-bit sample size.
• Type of sample size chosen for this audio
recording was also influenced by the quality of
sound card – 16 bit or 8 bit.

13. Factors Affecting the Quality Audio
(Cont.)
3.0 Channel
• There are two types of channels are often used in
audio recording:-
1. Mono
2. Stereo

14. Audio File Format
1.0 Audio Interchange File Format (AIFF and AIF)
• often used in computer systems of the Macintosh,
IBM and IBM-compatible.
• It holds a variety of different levels of sample size
(up to 32 bits).
• AIFF formats are usually not able to perform data
compression as AIFF files are usually larger than
other formats.

15. Audio File Format (Cont.)
2.0 Musical Instrument Digital Interface (MID,
MIDI, and MFF)
• format adopted around the world aim to keep the
audio from the types of MIDI.
• MIDI is the standard language used for
communication between musical instruments and
computers.
• This means that a musician can use electronic
keys, guitar and other MIDI equipment to
synthesizing audio to be connected to a personal
computer.

16. Audio File Format (Cont.)
3.0 Resource Interchange File Format (RIFF)
• This file format introduced by Microsoft and it may
contain various types of data including audio in form
of wave as well as MIDI.
4.0 Sound (SND)
• This file format was introduced by Apple and only
used for audio with 8-bit sample size.

17. Audio File Format (Cont.)
5.0 W ave (W AV)
• This file format most widely used.
• It was developed by Microsoft and can support
recording with sample size up to 8-bit and 16 bits
(mono and stereo).
• WAV files are usually large and depends on the
length of the recorded audio as well as the
sampling rate used for recording.

18. Audio File Format (Cont.)
6.0 Sun Audio (AU)
• It introduced specially for Sun Microsystems
workstations.
• It is 16 bit audio formats compressed, and are used
for the purpose of dissemination through the
Internet.
7.0 Real Audio or Real Media (RAM and RA)
• It is the most common file format used for audio
transmission via the Internet directly.

19. Audio File Format (Cont.)
8.0 MPEG Level 3 (MP3)
• audio file format that is increasingly popular,
especially for the purpose of online distribution of
music via the Internet.
• It has a good file compression technique can
compress audio up to size 45 MB in wav format to
about 4 MB only in MP3 format.

20. Storage Management
• Generally there are two main methods of of digital
audio data, namely:
1. The wave (Waveform Audio).
2. Musical Instrument Digital Interface (MIDI).

21. Storage Management (Cont.)
1.0 Waveform Audio
• This is the audio that was recorded in digital
form and stored in secondary storage.
• This audio is then played back through the
existing sound card in a computer system.
• Wave contains samples of the amplitude
(height of the voice) of audio taken at a
specified time (frequency) and then played
back at an appropriate rate.

22. Storage Management (Cont.)
2.0 MIDI
• It is actually not an audio format.
• It is mostly a form of the interface to produce
an audio.
• This audio is then stored in MIDI format.
• MIDI sound is produced by pressure on the
keyboard will be encoded as a series of
instructions and finally stored as a file and the
music score can be sent from computer to
another electronic equipment.