chapter 2 acoustics: definition and scope jean-louis...
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© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 1
Chapter 2 Acoustics: Definition and Scope Jean-Louis Migeot
1. Definitions: sound and acoustics
2. Why is acoustics important ?
3. Acoustics: a very broad research field !
1. Linear vs. non-linear
2. Aero- vs. vibro-acoustics
3. A few applications of ultrasounds
4. More acoustics research topics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 2
Chapter 2 Acoustics: Definition and Scope Jean-Louis Migeot
1. Definitions: sound and acoustics
2. Why is acoustics important ?
3. Acoustics: a very broad research field !
1. Linear vs. non-linear
2. Aero- vs. vibro-acoustics
3. A few applications of ultrasounds
4. More acoustics research topics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 3
What is a sound ?
A sound is a small and rapid fluctuation of pressure around a mean value.
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 4
Mean value
The mean value is either the atmospheric or the hydrostatic pressure
Atmospheric pressure changes with altitude
Hydrostatic pressure
changes with depth
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 5
Small fluctuation: how small ?
0
20,000
40,000
60,000
80,000
100,000
120,000
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
Pre
ssio
n t
ota
le (
[Pa]
)
Temps (unités arbitraires)
0
20,000
40,000
60,000
80,000
100,000
120,000
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
Pre
ssio
n t
ota
le (
[Pa]
)
Temps (unités arbitraires)
0
20,000
40,000
60,000
80,000
100,000
120,000
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
Pre
ssio
n t
ota
le (
[Pa]
)
Temps (unités arbitraires)
0
20,000
40,000
60,000
80,000
100,000
120,000
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
Pre
ssio
n t
ota
le (
[Pa]
)
Temps (unités arbitraires)
100 dB
160 dB
Time (arbitrary units)
Time (arbitrary units)
Tota
l pre
ssu
re (
[Pa]
) To
tal p
ress
ure
([P
a])
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 6
Rapid fluctuation: how fast ?
1 10 3 10 6 10 9 10 12
20 Hz 16 kHz 1 GHz
Sound Ultrasound Hypersound Infrasound
220 Hz A(3)
440 Hz A(4)
880 Hz A(5)
1760 Hz A(6)
110 Hz A(2)
55 Hz A(1)
27.5 Hz A(0)
3520 Hz A(7)
4186 Hz Do(8)
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 7
A typical (stereo) sound recording
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 8
Range of audible frequencies
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 9
Noise (negative) vs. sound (general)
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 10
Acoustics
Acoustics is concerned with pressure waves in air but also
in water (underwater acoustics)
in any fluid (e.g. transformer oil)
in any solid (structure-borne sound propagation in vehicles and buildings, P-waves in geodynamics)
Acoustics is concerned with 4 aspects of sounds:
production
propagation
reception and perception
effect on the propagation media
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 11
The three topics of engineering acoustics
Usually sound has no lasting effects on its propagation media
Acoustical engineers are primarily concerned with three aspects of sounds:
its production by a source -> physics of the source (vibration, turbulence, …)
its perception or recording by a receiver -> physiology of the ear, physics of microphones, …
the propagation from the source to the receiver -> propagation, reflection, attenuation, …
Source Path Receiver
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 12
Chapter 2 Acoustics: Definition and Scope Jean-Louis Migeot
1. Definitions: sound and acoustics
2. Why is acoustics important ?
3. Acoustics: a very broad research field !
1. Linear vs. non-linear
2. Aero- vs. vibro-acoustics
3. A few applications of ultrasounds
4. More acoustics research topics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 13
Why acoustics ? Noise is annoying !
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 14
Why acoustics ? Noise performance is a purchase criteria !
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 15
Why acoustics ? Stringent standards apply !
© CRITT M2A
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 16
European Pass-by noise regulation
Pass-by noise engineering: a review of different transfer path analysis techniques - K. Janssens et al. – ISMA 2014
2016
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 17
Why acoustics ? Noise performance may mean success or failure !
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 18
Chapter 2 Acoustics: Definition and Scope Jean-Louis Migeot
1. Definitions: sound and acoustics
2. Why is acoustics important ?
3. Acoustics: a very broad research field !
1. Linear vs. non-linear
2. Aero- vs. vibro-acoustics
3. A few applications of ultrasounds
4. More acoustics research topics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 19
Fields of acoustics
Lindsay R.B., JASA., 36:2242 (1964) cited by Pierce A.D. , Acoustics, Acoustical Society of America and American Institute of Physics (1994).
Hearing
Bioacoustics
Oceanography
Physics of Earth and
Atmosphere
Electrical &Chemical
Mechanical
Architectural
Visual Arts
Music
Speech
Psychology
Physiology
Medicine
EarthSciences
Engineering
ArtsLife
Sciences
Seismic wavesSound in theatmosphere
UnderwaterSound
Electro-acoustics
Ultra-sonics
Shock andVibrations
Room andTheatre
Acoustics
Musical scales& Instruments
Psycho-acoustics
Com-muni-cation
FundamentalPhysical
Acoustics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 20
Classification of the Acoustical Society of America
Categories based on the underlying physics or technique:
General linear acoustics
Nonlinear acoustics
Aeroacoustics
Structural acoustics Vibrations
Ultrasonics, Physical effects of sound
Categories related to life science:
Physiological acoustics
Speech-Production, Perception, Processing
Psychological acoustics
Bioacoustics
Categories based on applications:
Architectural acoustics
Music and musical instruments
Noise, its effects and control
Electro-acoustics
Underwater acoustics
Transverse categories
Transduction; Acoustical measurements
Acoustic signal processing
Audio Engineering
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 21
Chapter 2 Acoustics: Definition and Scope Jean-Louis Migeot
1. Definitions: sound and acoustics
2. Why is acoustics important ?
3. Acoustics: a very broad research field !
1. Linear vs. non-linear
2. Aero- vs. vibro-acoustics
3. A few applications of ultrasounds
4. More acoustics research topics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 22
A 2*B
p(A+2*B) = p(A)+2*p(B)
Linearity ?
Linearity means:
Superposition pA + pB = pA+B
Proportionality pkB=k.pB
The immense majority of acoustic phenomena are linear
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 23
Linear vs. non-linear acoustics
Non-linear phenomena appear when:
Sound levels are very high (jet engines, power ultrasound) ~ 150dB
The source amplitude depends on induced acoustic field (burner noise)
The mechanical properties of the acoustic media change with the sound field (acoustic cavitation)
Examples
Sonic Boom
Acoustic levitation
Sonochemistry
Sonoluminescence
Acoustic streaming
It is in the field of ultrasound that most non-linear acoustic phenomena are encountered
© Wikipedia – Sonic Boom
© http://www.hashmoder.com/ 2010/01/20/acoustic-levitation/
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 24
Sonoluminescence
Felipe Gaitan Larry Crum
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 25
Sonochemistry: improving chemical yield with ultrasounds
© Jean-Louis Migeot, ASA, 1998
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 26
Acoustic streaming
Olivier Dahlem &
Véronique Halloin (1998)
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 27
Science, scientists and engineers in motion pictures ...
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 28
Chapter 2 Acoustics: Definition and Scope Jean-Louis Migeot
1. Definitions: sound and acoustics
2. Why is acoustics important ?
3. Acoustics: a very broad research field !
1. Linear vs. non-linear
2. Aero- vs. vibro-acoustics
3. A few applications of ultrasounds
4. More acoustics research topics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 29
Aeroacoustics vs. vibro-acoustics
Aero-acoustics:
generation of noise by flows:
• turbulents flows (jets, boundary layer)
• turbomachinery flow
propagation of sound waves in a moving fluid (convected propagation)
flow induced by sound in a dissipative fluid (streaming).
Vibro-acoustics = Sound radiation by vibrating structures:
cars: powertrain, body, transmission, alternator
machines: stamping and forging, printing, electrical devices
home appliances: vacuum cleaner, dishwasher, washing machines
electronics: television, computers
…
An acoustic phenomenon may always be categorized as aeroacoustics or vibro-acoustics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 30
Aero-acoustics
© ACTRAN / Free Field Technologies
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 31
Vibro-acoustics
© ACTRAN / Free Field Technologies
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 32
Chapter 2 Acoustics: Definition and Scope Jean-Louis Migeot
1. Definitions: sound and acoustics
2. Why is acoustics important ?
3. Acoustics: a very broad research field !
1. Linear vs. non-linear
2. Aero- vs. vibro-acoustics
3. A few applications of ultrasounds
4. More acoustics research topics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 33
Ultrasounds – Non-destructive Testing
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 34
Ultrasounds in Production Engineering
Emulsification
Homogenization
Welding
Cleaning
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 35
Ultrasounds – Medical Applications
Echography
Cautery
Lithotripsy
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 36
Breaking glass …
The Fat Lady guarding the entrance of Gryffindor Tower © Harry Potter and The Prisoner of Azkaban
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 37
Tif & Tondu vs. M. Choc
CHOC !
What are I have activated my
ultrasound system: the
house will collapse.
Good luck !
you doing !
Tif et Tondu © Will
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 38
Calculus’ sonic weapon
Tintin, The Calculus Affair © Hergé - Moulinsart
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 39
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 40
Chapter 2 Acoustics: Definition and Scope Jean-Louis Migeot
1. Definitions: sound and acoustics
2. Why is acoustics important ?
3. Acoustics: a very broad research field !
1. Linear vs. non-linear
2. Aero- vs. vibro-acoustics
3. A few applications of ultrasounds
4. More acoustics research topics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 41
Classification of the Acoustical Society of America
Categories based on the underlying physics or technique:
General linear acoustics
Nonlinear acoustics
Aeroacoustics
Structural acoustics Vibrations
Ultrasonics, Physical effects of sound
Categories related to life science:
Physiological acoustics
Speech-Production, Perception, Processing
Psychological acoustics
Bioacoustics
Categories based on applications:
Architectural acoustics
Music and musical instruments
Noise, its effects and control
Electro-acoustics
Underwater acoustics
Transverse categories
Transduction; Acoustical measurements
Acoustic signal processing
Audio Engineering
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 42
Physiological acoustics: speaking and hearing
© Blausen.com staff. "Blausen gallery 2014“
Wikiversity Journal of Medicine. © http://training.seer.cancer.gov/head-neck/anatomy/overview.html
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 43
Sense of hearing – Auditory Transduction
Brandon Pletsch
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 44
Psycho-acoustics
Effect of personal, environmental and other non-acoustical factors on noise perception
cumulative aspect of noise nuisance
effect of stress, fatigue, illness, lack of sleep, sex, age, education
perceptive coupling: vibratory, visual
psychological or physical factors (ex: announcement effect)
Differences between objective and subjective noise measures:
definition of psycho-acoustical indices: loudness, pitch, …
Sound quality
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 45
Bio-acoustics: snapping shrimp
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 46
Room and building acoustics
© MJM ACOUSTICAL CONSULTANTS INC © DOUGLAS MICHAEL VERSAGLI
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 47
Electro-acoustics and micro-acoustics
Electro-acoustics
loudspeakers
headsets
microphones
telephones
Micro-acoustics (visco-thermal loss effects in small cavities, ducts and layers)
auditory prosthesis
mobile phones
inkjet printers
solar panels
© ACTRAN / Free Field Technologies
© http://www.hearingaidopinion.com
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 48
Underwater acoustics: civil applications
Acoustic thermometry
Seafloor survey
http://npal.ucsd.edu/thermometry/index.htm
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 49
Underwater acoustics: military applications
Torpedo guiding system
Identification of submarines and other vessels by their ultrasonic echo
Non lethal weapons for underwater warfare
© Ultra Electronics
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 50
Transduction, metrology, signal processing
Microphones, hydrophones, intensity probes
Active materials:
piezo-electric
magneto-strictive
electro-strictive
Measurement techniques:
sound measurement
intensimetry
acoustic holography
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 51
Key Takeaways
Acoustics includes sound production-propagation-perception.
Noise is defined by the time history of acoustic pressure
Acoustics is a very broad topic ranging from very practical to rather exotic fields of research. Key differences between sub-domains:
vibro- vs. aero-acoustics
linear vs. non-linear
audible acoustics vs. ultrasonics
Our focus in the course will be on audible sound propagation.
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 52
Get your hands dirty !
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 53
Think for yourself
Take a few minutes to answer the following questions for yourself:
why is acoustics important for your own company ?
• customer (user)
• citizens
• standards compliance
who (which department(s)) is (are) in charge of the design part, the experimental part, the standards compliance part ?
how do the various actors work together ?
list the tools, technologies, partners that are used by your company to improve your product’s acoustic performance
© Jean-Louis Migeot – MSC Software – Free Field Technologies – Université Libre de Bruxelles – Conservatoire Royal de Musique de Liège – IJK Numerics 54
Chapter 2 Acoustics: Definition and Scope Jean-Louis Migeot
1. What is a sound ?
2. Definition of acoustics
3. Why is acoustic so important ?
4. The wide field of acoustics
1. Linear vs. non-linear
2. Aero- vs. vibro-acoustics
3. A few applications of ultrasounds
4. More acoustics research topics