Post on 07-Aug-2020
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 1
[701-0662-00 V]
Environmental Impacts, Threshold Levels and
Health Effects
Lecture 7: Noise - Part 1 (01.04.2020)
Mark Brink
ETH Zürich
D-USYS
Homepage:
http://www.noise.ethz.ch/ei/
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 2
EmissionPerception
Effects
Limitation
AssessmentNoise abatement
Rating of noise
Noise regulation
(policy)
Immission
Sound & Noise
Topics of the next six lectures
Hearing
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 3
Overview of today’s lecture
► Physical basics of sound
► Sound generation, propagation, and perception (short intro)
► Frequency and wavelength
► Types of waves
► Sound pressure and sound pressure level
► Time and frequency domain
► The Decibel (dB)
► Physiological basis of hearing
► Anatomy of the ear
► Outer ear, middle era, inner ear
► Theories of auditory perception
► The cochlea
► Perceptual organization of sound
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 4
Physical basics of sound
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 5
Sound generation, propagation, and perception
What is sound?
• Sound is a disturbance that propagates through a medium
that has properties of inertia (mass) and elasticity.
• The medium by which the audible waves are transmitted
is air or water, or even solid bodies (e.g. a wall, a window,
the ceiling of your apartment...)
• Sound propagation is simply the molecular transfer of
motional energy (Hence: sound cannot pass through a
vacuum).
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 6
Sound generation, propagation, and perception
How is it generated?
• By mechanical motion, e.g. from a loudspeaker
membrane, from a vibrating string... etc.
• If the motion is periodical, the sound has (one or
more) distinguishable frequencies
waveform of one second of sound
waveform of 12 seconds of sound
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 7
Sound generation, propagation, and perception
Why can we hear it?
• Because the energy contained in a sound wave puts
the eardrum into vibrational motion
• the eardrum translates the energy of the wave trough
the ossicles of the middle ear onto the cochlea in the
inner ear and the cochlear hair cells
• the hair cells produce neuronal action potentials
which travel through the auditory nerve to the brain
• ... the brain interprets these action potentials as
"sound"
• ... more about auditory perception will follow soon..
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 8
Sound generation and propagationSound as longitudinal compression wave
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 9
c
f CAir ≈ 340 m/s
CWater ≈ 1400 m/s
place x
pre
ssu
re c
han
ge
Sound generation and propagation
Wavelength and frequency
Propagation speeds:
standard pitch 'A' (440 Hz) → λ = 0.77 m (in air)
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 10
wavelength (λ, lambda)
movement
of air moleculesmovement
of tines
tuning fork
sound propagation
high pressurelow pressure
sound pressure
atmospheric pressure
place
medium (air, water)
Sound generation and propagation
Summary
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 11
Types of sound waves (in the time and frequency domain)
4 8 12 16 20
4 8 12 16 20
4 8 12 16 20
Zeit [ms]
Sc
ha
lld
ruc
k [
Pa
]
31 125 500 2000 8000
31 125 500 2000 8000
31 125 500 2000 8000
Frequenz [Hz]
Te
rzb
an
dp
eg
el
[dB
]
Pure tone ("Reinton")
Complex sound ("Klang")
Noise ("Rauschen")
white: pink:
So
un
d p
res
su
reS
ou
nd
pre
ss
ure
So
un
d p
res
su
re
Time [ms] Frequency [Hz]
440 Hz
880 Hz
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 12
Time domain: one wave
-4
-3
-2
-1
0
1
2
3
4
Wave #1
Time
So
un
d p
ress
ure
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 13
Time domain: two waves
-4
-3
-2
-1
0
1
2
3
4 Wave #1
Wave #2
Time
So
un
d p
ress
ure
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 14
Time domain: three waves
-4
-3
-2
-1
0
1
2
3
4Wave #1
Wave #2
Wave #3
Time
So
un
d p
ress
ure
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 15
Time domain: the sum signal
-4
-3
-2
-1
0
1
2
3
4Wave #1
Wave #2
Wave #3
Sum signal
Time
So
un
d p
ress
ure
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 16
Frequency domain: the spectrum of the sum signal
FFT spectrum of the sum signal
Mag
nit
ud
e
Frequency
Wave #3
Wave #2
Wave #1
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 17
Demo-Excel sheetdownload at www.noise.ethz.ch/ei
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 18
Range of frequencies
audible frequency
range
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 19
Sound pressure - time courseS
ou
nd
pre
ss
ure
p in
Pa
atmospheric pressure (ca. 100‘000 Pascal [Pa])
1 Pa = Force of 1 Newton per square meter = 1 N/m2
Time t
Sound pressure fluctuations are very small in
relation to the standing atmospheric pressure
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 20
Peff = Effektivwert = Root mean square (RMS)
Sc
ha
lld
ruc
k p
in
Pa
Zeit t
Schalldruck pi zum Zeitpunt ti in Pa
atmosphärischer Luftdruck
Root mean square value
Atmospheric pressure
Sound p
ressure
in P
a
Sound pressure in Pa
ger. “Effektivwert”
1RMS =
2for a sine wave:
Root Mean Square (RMS) value= a measure of energy of a sound wave
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 21
Transmission, Reflection and Absorption
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 22
Anechoic chamber (A lot of absorption, no reflections)
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 23
Echo chamber (No absorption, a lot of reflections...)
Echo chamber at Empa in Dübendorf
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 24
Sound pressure: Pressure fluctuations in the air that occur in
a point in space as the sound pressure waves travel
Unit: Pascal (Pa) = 1 N/m2
→ depending on the location of the receiver relative to source
Sound power: Sound energy that a sound source produces
per time unit
Unit: Watt
→ Independent of the location of the receiver
Sound pressure and sound pressure level
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 25
Sound pressure level Lp [in dB]: is a logarithmic
measure of the sound pressure of a sound relative to a
reference value. It indicates “how many times” larger is
the measured sound pressure relative to the pressure at
the hearing threshold
Unit: Decibel [dB]
Reference pressure p0: 0.00002 Pa (= Hearing threshold @ 1000Hz)
Threshold of pain: 20 Pa
2
10 2
0
pL 10 log
p
[dB]
Sound pressure level
Note: p is the RMS value in Pascal
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 26
Sound
pressure [Pa]
Reference sound
pressure [Pa]
Ratio of
squares
Logarithm Level
[dB]
0.00002 0.00002 1 0 x 10 = 0
0.0002 0.00002 100 2 x 10 = 20
0.002 0.00002 10000 4 x 10 = 40
0.02 0.00002 1000000 6 x 10 = 60
0.2 0.00002 100000000 8 x 10 = 80
2 0.00002 10000000000 10 x 10 = 100
20 0.00002 1E+12 12 x 10 = 120
200 0.00002 1E+14 14 x 10 = 140
Threshold of pain
Hearing threshold
Calculation of the sound pressure level
Bel Deci-bel
Namesake: A. Graham Bell
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 27
So
un
d p
ressu
re l
evel
0
20
40
60
80
100
120
140
160
[ Pa ] [ W/m2 ]
10-12
10-10
10-8
10-6
10-4
0.01
1
100
1000
Whisper
Acute irreversible damage
Threshold of pain
Danger to hearing
Speech understandability
Hearing threshold
[ dB ]
Effects:
0.00002
0.0002
0.002
0.02
0.2
2
20
200
2000
So
un
d in
ten
sit
y
Decibel scaleS
ou
nd
pre
ssu
re
Firecracker
Jet taking off
Rock concert
Mp3 player
Rehearsal room
Jackhammer
Noisy road traffic
Conversation
Concert hall (empty)
Source:
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 28
80 dB 80 dB+ = 83 dB
Summation:
Averaging:
0 dB + 0 dB = 3 dB
Decibel arithmetic
n
N0.1 L
10
n 1
L 10 log 10
n
N0.1 L
n 1
10
10
L 10 logN
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 29
Changes of sound pressure levelQualitative perception
Change of level Perception
1-2 dB barely recognizable change
2-5 dB recognizable change
5-10 dB well recognizable change
10-20 dB large, convincing change
> 20 dB very large change
440 Hz, each tone 1 dB lower
440 Hz, each tone 3 dB lower
440 Hz, each tone 5 dB lower
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 30
Physiology of hearing
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 31
bone conduction
air
conduction
Cochlea
eardrum
ear canal
equilibrium organ
Eustachian
tube
Anatomy of the ear
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 32
outer ear middle ear inner ear
eustachian tube
ossicles
(ger. "Gehörknöchelchen")
cochlea
eardrum
oval window
round window
sound pressure
Anatomy of the ear
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 33
mastoid
Comparison of the perception of
sounds, as transmitted by air or
by bone conduction (through
mastoid).
Procedure:
(1) Put tuning fork on mastoid
When the tone disappears...
(2) hold tuning fork close to the ear
Judge result:
If tone is still audible → everything ok
if not, → Conductive hearing loss
(1)
(2)
Rinne test
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 34
Stirrup (tiniest bone of
skeleton)
eardrum
roundwindow
oval window
basilarmembrane
Anvil (ger. Amboss)
Stirrup (ger. Steigbügel)
Hammer (ger. Hammer)
pivotpoint
eustachian tube
Anatomy of the middle ear
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 35
inner ear (Cochlea)outer ear
airborne sound liquidborne sound
middle ear
eardrumoval window
Large area, weak force small area, strong force
Impedance matching
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 36
Base
Apex
in mammals: spiral form
in birds, reptiles: stretched out
Inner ear: cochlea
round window
oval window
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 37
Resonance in the Cochlea („place coding“)
high tone
low tone
von Helmholtz
von Békécy
Place theory of pitch perception
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 38
Basilar membraneTraveling wave
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 39
Basilar membraneTraveling wave characteristics
• The wave always starts at the base of the cochlea
and moves towards the apex
• Its amplitude changes as it traverses the length of
the cochlea
• The position along the basilar membrane at which
its amplitude is highest depends on the frequency
of the stimulus
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 40
Apex
Base (oval window)
440 Hz
880 Hz
1320 Hz
low frequencies
high frequencies
outer
ear
middle
ear
Basilar membraneFrequency decomposition
stiff, narrow
less stiff, wider
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 41
oval window
round window
basilar membrane
Cross section of cochlea, organ of Corti
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 42
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 43
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 44
“The movie shows an outer hair cell which has been patch clamped using a whole cell
recording pipette at its basal end. This allows the membrane potential of the cell to be
varied. The low frequency envelope of RatC is played into the stimulus input socket of
the patch amplifier, with a peak-to-peak amplitude of about 100 mV. The hair cell
changes it’s length.
Source: http://www.physiol.ucl.ac.uk/ashmore/
outer hair cellsinner hair cells
The “dancing hair cell” (Jonathan Ashmore, 1987)
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 45
Sound localization cuesInteraural time delay
Interaural level difference
Convolutions of the outer ear
D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 46
1
2
3
4
5
6
7
"Gestalt"-Principles of auditory perception (Examples)
Auditory figure-ground perception