SOUND
What is SOUND?
Sound comprises the spoken word, voices, music and even
noise.
It is a complex relationship involving:
a vibrating object (sound source)
a transmission medium (usually air)
a receiver (ear) and;
a preceptor (brain).
The Power of Sound
Something vibrates Waves of pressure Ear drums will translate
in the air these changes in wave
Forms as sound
Sound pressure is measured in dB
(decibel)
Sound waves are known as waveforms.
Decibel Table
Example of Waveforms
Piano
Pan flute
Snare drum
Sound
A pleasant sound has a regular wave pattern. The
pattern is repeated over and over.
But the waves of noise are irregular. They do not have
a repeated pattern.
Characteristic of Sound Waves
Sound is described in terms of two
characteristics:
Frequency (or pitch)
Amplitude (or loudness)
Frequency
Frequency is a measure of how many vibrations occur in one
second. This is measured in Hertz (abbreviation Hz) and directly
corresponds to the pitch of a sound.
The more frequent vibration occurs the higher the pitch of the sound.
Low pitch High pitch
Optimally, people can hear from 20 Hz to 20,000 Hz (20 kHz)
Sounds below 20 Hz are infrasonic
sounds above 20 kHz are ultrasonic.
Amplitude
Amplitude is the maximum displacement of a wave from an
equilibrium position.
The louder a sound, the more energy it has. This means loud sounds
have a large amplitude.
Quiet Loud
Low amplitude High Amplitude
The amplitude relates to how loud a sound is.
Characteristic of Sound Waves
Time for one cycle
Amplitude wavelength distance
along wave
Cycle
Audio Recording Software
WINDOWS
Sound Recorders for Windows
Both Macintosh and Windows PC platform have the default
sound.
This basic application could:
Record our own sounds
Edit & mix *.wav files
Simple Splicing and assembly
Increase volume & speed of *.wav files
Reverse the sound.
Add Echo effects
Some XP Version also provide wav to mp3 conversion.
Analogue to Digital Audio
Analogue audio
The name for an electronic signal that carries its information of sound as
continuous fluctuating voltage value.
non digital tape or audio tape recording of sound.
Digitizing
the process of converting an analog signal to a digital one.
A sound is recorded by making a measurement of the amplitude of the
sound at regular intervals which are defined by the "sample rate".
The act of taking the measurement is often called "sampling" and each
measurement is called a "sample point".
Capture & Playback of Digital Audio
Air pressure
variations Digital to
Analogue
Convert Converter
s back
into DAC
Captured via voltage
microphone
Signal is
converted into
binary
Analogue (discrete form)
to Digital ADC 0101001101 Air pressure
Converter 0110101111 variations
Recording Audio Files
Recording Audio Files on the pc
Uses either:
i. Microphone
connect microphone to the microphone port and record using
sound recorder
Recording Audio Files
ii. CD-ROM Drive
Move music files from CD to hard drive or;
Play the cd and then record using the sound recorder.
iii. Line-in
pressing play on the audio source, which is connected to
the computer’s audio line-in socket. Record using the
sound recorder.
Line in port
on the pc
Audio cable
Digital Audio
Digital audio data is the representation of sound, stored in the
form of samples point.
Quality of digital recording depends on the sampling rate, that is,
the number of samples point taken per second (Hz).
High Sampling Rate Samples stored in digital
form
waveform
Low Sampling Rate
Digital Audio
The three sampling frequencies most often used in multimedia
are 44.1 kHz, 22.05 kHz and 11.025 kHz.
The higher the sampling rate, the more the measurements are
taken (better quality).
The lower the sampling rate, the lesser the measurements are
taken (low quality).
High Sampling Rate Low Sampling Rate
Digital Audio
Quality factors for digital audio file :
1. Sampling Rate
2. Sample Size (resolution)
the number of bits used to record the value of a sample
in a digitized signal.
Sampling Rate Sample size
Digital Audio
Other than that, it also depends on:
The quality of original audio source.
The quality of capture device &
supporting hardware.
The characteristics used for capture.
The capability of the playback environment.
Digital Audio
More advanced Digital audio editing software:
One of the most powerful and professional PC-based
packages is a tool called Adobe Audition
Others audio editing software:
Sound Forge
COOL Edit Pro
Gold Wave
PROSONIQ SonicWORX
Audio File Formats
MIDI
*.MID, *.KAR, *.MIDI, *.SMF
AUDIO DIGITAL
WINDOWS *.WAV
MACINTOSH *.AIFF
UNIX *.AU
REALAUDIO *.RA
MPEG3 *.MP3
Factors considered before adding
Sound to MM Project
1. File formats compatible with multimedia authoring
software being used along with delivery mediums,
must be determined.
2. Sound playback capabilities offered by end user’s
system must be studied.
3. The type of sound, whether background music,
special sound effects, or spoken dialog, must be
decided.
4. Digital audio or MIDI data should be selected on
the basis of the location and time of use.
Function of Audio
1. Content/ information
2. Background music
3. Ambience
Advantages & Disadvantages of Using Audio
Sound adds life to any multimedia application
and plays important role in effective
marketing presentations.
Advantages
Ensure important information is noticed.
Add interest.
Can communicate more directly than other
media.
Advantages & Disadvantages of Using Audio
Disadvantages
Easily overused.
Requires special equipment for quality
production.
Not as memorable as visual media.
General Check-up
What is the standard measurement of sound
pressure?
What is the range of frequencies that humans
can hear?
Describe the two (2) characteristics of sound
waves.
State the default sound format in Windows,
Macintosh and UNIX operating systems.
