BPC: Art and Computation – Summer 2007 Digital Media - Audio Glenn Bresnahan [email protected].
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Transcript of BPC: Art and Computation – Summer 2007 Digital Media - Audio Glenn Bresnahan [email protected].
BPC: Art and Computation – Summer 2007BPC: Art and Computation – Summer 2007
Digital Media - AudioDigital Media - Audio
Glenn Bresnahan
BPC: Art and Computation – Summer 2007 2
OverviewOverview
Principles and properties of sound and perception – Lessons 5.a & 5.b - 1 class each
• Glenn Bresnahan, Robert Putnam
– Lectures & demonstrations Sound recording and digital editing
– Lesson 6 - 3 classes• Manny Rettinger
– Studio and field work, instruction+lab
BPC: Art and Computation – Summer 2007 3
SynopsisSynopsis
Physical properties Mathematical properties of sine waves
Representation of functions as graphs of sound Characteristics of real sounds Analog and digital representation and
recording of sound Field and studio recording techniques and
equipment Digital audio manipulation and editing
BPC: Art and Computation – Summer 2007 4
Digital Audio: Sound and Hearing (5.a)Digital Audio: Sound and Hearing (5.a)
Objectives– Understanding of the basics physics of
sound• Understanding the fundamentals of waves
– Mathematically– Physical properties of sound waves– Composition of complex waves from sine waves
• Representation and transductions of signals
– Biophysics of human hearing
BPC: Art and Computation – Summer 2007 5
Sound wave conceptsSound wave concepts
Mathematical properties of (sine) waves– Amplitude, wavelength, frequency, period and speed– Representation: function graphs/plots
Principles of sound– Vibrations & resonance– Physical properties of sound (frequency, speed, sound
pressure levels) Real sounds
– Absorption and reflection (reverberation)– Compound frequencies
Signal transduction – Converting between SPL and current
BPC: Art and Computation – Summer 2007 6
Sound waves approachSound waves approach
Analogies to cyclical phenomena – Waves in water, moon phases, sun
rise/set, tides
BPC: Art and Computation – Summer 2007 7
Moon phasesMoon phases
Moon Phase
0%
25%
50%
75%
100%
Date
Per
cen
tag
e V
isib
le (
ph
ase)
BPC: Art and Computation – Summer 2007 8
Cause of tidesCause of tides
Gravity from moon and sun
365 days
27.3 days (29.5 days)
New moon
Full moon
1 day
BPC: Art and Computation – Summer 2007 9
Sunrise and sunsetSunrise and sunset
Sunrise - Sunset Times
0.00
4.00
8.00
12.00
16.00
20.00
24.00
Date
Hour
of D
ay Sunrise Time
Sunset Time
Daylight Hours
8.00
9.00
10.00
11.00
12.00
13.00
14.00
15.00
16.00
Date
Ho
urs
of D
aylig
ht
solstice
solstice
BPC: Art and Computation – Summer 2007 10
Sound and vibrationSound and vibration
Demonstration with real instruments
BPC: Art and Computation – Summer 2007 11
Transverse waves in time and spaceTransverse waves in time and space
string
Energy(pluck)
vibration
WaveWaveAir pressure level
BPC: Art and Computation – Summer 2007 12
Combinations of wavesCombinations of waves
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
1 26 51 76 101 126
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
1 26 51 76 101 126
BPC: Art and Computation – Summer 2007 13
Properties of sound – real soundsProperties of sound – real sounds
BPC: Art and Computation – Summer 2007 14
How do we hear?How do we hear?
Sound waves move through the air from the sound source to the ear
BPC: Art and Computation – Summer 2007 15
Anatomy of the earAnatomy of the ear
BPC: Art and Computation – Summer 2007 16
Haircells and neural firingsHaircells and neural firings
BPC: Art and Computation – Summer 2007 17
Binaural hearing - why two ears?Binaural hearing - why two ears?
Two ears, so we can identify locations of sounds– Time difference– Intensity difference– Sound color difference (caused by
movement of sound around head and shoulders)
BPC: Art and Computation – Summer 2007 18
Lecture MaterialsLecture Materials
Digital Audio Parts 1 & 2:
http://scv.bu.edu/BPC/http://scv.bu.edu/BPC/MaterialsFall06/lectures/BPC-Class-MaterialsFall06/lectures/BPC-Class-DigitalMedia-Audio.pptDigitalMedia-Audio.ppt