SOUND ELEMENT Flashcards
is a physical phenomenon produced by the vibration of matter and
transmitted as waves.
Sound
the perception of sound by human beings is a very complex process. It involves three systems
- the source which emits sound;
- the medium through which the sound propagates;
- the detector which receives and interprets the sound.
simplest sound we
can hear is a
sine wave
Sound waves can be characterized by the following attributes:
- Period
- Frequency
- Amplitude
- Bandwidth
- Pitch
- Loudness
- Dynamic
is the interval at which a periodic
signal repeats regularly.
Period
is a perception of sound by
human beings, it measures how ‘high’ is
the sound as it is perceived by a
listener.
Pitch
measures a physical
property of a wave.
Frequency
Musical instruments are tuned to produce
a set of
fixed pitches
0 – 20 Hz
Infra-sound
20 – 20 kHz
Human hearing range
20 kHz – 1 GHz
Ultrasound
1 GHz – 10 THz
Hypersound
is the measure of sound levels.
Amplitude
If the intensity of a sound is 1watt=m2
, we may start feel the sound. The ear may be damaged. This is known as the
threshold of feeling.
If the intensity is 10-12watt=m2
, we may just be able to hear it. This is known as the
threshold of
hearing.
The relative intensity of two different sounds is measured
using the unit
Bel or more commonly deciBel (dB).
means the change in sound
levels.
Dynamic range
the range of frequencies a
device can produce, or a human can hear.
Bandwidth
Sound waves are ___ while computers are good at handling discrete numbers.
continuous
Each sample is represented by a number, the
‘code’.
In order to store a sound wave in a computer, samples of the wave are taken.
* Each sample is represented by a number, the ‘code’.
* This process is known as ___
digitization
This method of digitizing sound is known as
pulse code modulation (PCM)
According to ___ ___ ___, in order to capture all audible frequency
components of a sound, i.e., up to 20kHz, we need to set the sampling to at least twice of this.
Nyquist sampling theorem
most popular sampling rate for high quality sound is
4410Hz
The most commonly use digital sound format in
Windows systems is
.wav
Sound is stored in .wav as digital samples
known as
Pulse Code Modulation (PCM)
use Adaptive Delta Pulse Code Modulation
(ADPCM).
.vox
MPEG-1 layer 3 audio
.mp3
is a proprietary format
RealAudio file
Recording and Digitizing sound:
analog-to-digital converter (ADC)
digital signal processor (DSP)
converts the analog sound signal into digital
samples.
analog-to-digital converter (ADC)
processes the sample, e.g. filtering, modulation,
compression, and so on.
digital signal processor (DSP)
Play back sound:
digital signal processor (DSP)
digital-to-analog converter (DAC)
processes the sample, e.g. decompression,
demodulation, and so on
digital signal processor (DSP)
converts the digital samples into sound signal
digital-to-analog converter (DAC)
controls the hardware device
Windows device driver
— the user’s interface to the hardware for configuring the
devices.
Device manager
- to combine sound from different sources
- to adjust the play back volume of sound sources
- to adjust the recording volume of sound sources
Mixer
— Windows has a simple Sound Recorder
Recording
The Windows Sound Recorder has a limiting editing
function, such as changing volume and speed, deleting part of
the sound.
Editing
There is a better way to generate high quality music. This is known as ____. It is a communication standard
developed in the early 1980s for electronic instruments and computers.
MIDI — Musical Instrument Digital Interface
is a standard specified by
MIDI Manufacturers Association.
General MIDI
The MIDI ports
on musical
in
OUT
THRU
— for receiving MIDI data
IN
— for outputting MIDI data that are
generated by the instrument
OUT
— for passing MIDI data to the next
instrument
THRU
Each MIDI files contains
a number of
CHUNKS
two types of
chunks
Header chunk
Track chunk
contains information
about the entire file
: the type of MIDI
file, number of tracks and the timing
.
Header chunk
— the actual data of MIDI
track
.
Track chunk
There three types of MIDI file
- 0 single multichannel track
- 1 one or more simultaneous track of
a sequence - 2 one or more sequentially independent
single -track patterns
two different types of envelop
Diminishing sound
Continuing sound
gradually
die out
- Diminishing sound —
sustain until
turned off
Continuing sound
THE
AMPLITUDE
ENVELOP
delay
attack
hold
decay
sustain
release
the time between when a key is played and when the
attack phase begins
Delay
the time from no sound to maximum amplitude
Attack
the time envelop will stay at the peak level before starting
the decay phase
Hold—
the time it takes the envelop to go from the peak level
to the sustain level
Decay
the level at which the envelop remains as long as a key
is held down
Sustain
— the time is takes for the sound to fade to nothing
Release —
Digital representation of physical
sound waves
Digital Audio
Abstract representation of
musical sounds and sound effects
MIDI
