Health Effects Lecture 7: Noise - Part 1 (01.04.2020) Mark Brink - - PowerPoint PPT Presentation

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

Emission Perception Effects Limitation Assessment Noise 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 propagation

Sound 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 pressure change

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

• f air molecules

movement

• f tines

tuning fork sound propagation high pressure low 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] Schalldruck [Pa]

31 125 500 2000 8000 31 125 500 2000 8000 31 125 500 2000 8000

Frequenz [Hz] Terzbandpegel [dB]

Pure tone ("Reinton") Complex sound ("Klang") Noise ("Rauschen")

white: pink:

Sound pressure Sound pressure Sound pressure

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

1 2 3 4

Wave #1

Time

Sound pressure

D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 13

Time domain: two waves

• 4
• 3
• 2
• 1

1 2 3 4

Wave #1 Wave #2

Time

Sound pressure

D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 14

Time domain: three waves

• 4
• 3
• 2
• 1

1 2 3 4

Wave #1 Wave #2 Wave #3

Time

Sound pressure

D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 15

Time domain: the sum signal

• 4
• 3
• 2
• 1

1 2 3 4

Wave #1 Wave #2 Wave #3 Sum signal

Time

Sound pressure

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

Magnitude Frequency

Wave #3 Wave #2 Wave #1

D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 17

Demo-Excel sheet

download 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 course

Sound pressure 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) Zeit t Schalldruck pi zum Zeitpunt ti in Pa atmosphärischer Luftdruck

Root mean square value Atmospheric pressure Sound pressure in Pa Sound pressure in Pa

• ger. “Effektivwert”

1 RMS = 2 for 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

p L 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 x 10 = 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

Sound pressure level

20 40 60 80 100 120 140 160

[ Pa ] [ W/m

2 ]

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

Sound intensity

Decibel scale

Sound pressure

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

N 0.1 L 10 n 1

L 10 log 10

 

       



n

N 0.1 L n 1 10

10 L 10 log N

 

             



D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 29

Changes of sound pressure level

Qualitative 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

• uter ear

middle ear inner ear

eustachian tube

• ssicles

(ger. "Gehörknöchelchen") cochlea eardrum

• val 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 round window

• val window

basilar membrane Anvil (ger. Amboss) Stirrup (ger. Steigbügel) Hammer (ger. Hammer) pivot point eustachian tube

Anatomy of the middle ear

D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 35

inner ear (Cochlea)

• uter ear

airborne sound liquidborne sound middle ear

eardrum

• val 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

• val 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 membrane

Traveling wave

D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 39

Basilar membrane

Traveling 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

• f 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

• uter

ear middle ear

Basilar membrane

Frequency decomposition

stiff, narrow less stiff, wider

D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 41

• val 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/

• uter hair cells

inner hair cells

The “dancing hair cell” (Jonathan Ashmore, 1987)

D-USYS • M. Brink • Environmental Impacts - Noise Part 1 Slide 45

Sound localization cues

Interaural 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