Rak-43.3415 Building Physics Design 2
ACOUSTICAL DESIGN
Autumn 2015
LECTURE 1
Introduction to Acoustical Design
Matias Remes, M.Sc FISE A acoustics
Course arrangements
Schedule
• Lectures (6) 8.9-13.10 Tue 16.15-20 in hall R2, main
themes:
–
–
–
–
–
–
8.9 Lecture 1: Introduction, basic concepts of acoustics
15.9 Lecture 2: Airborne sound insulation
22.9 Lecture 3: Impact sound insulation
29.9 Lecture 4: Room acoustics
6.10 Lecture 5: HVAC noise control, vibration isolation
13.10 Lecture 6: Traffic noise, guidelines and regulations
• Exercises (5) 14.9-12.10 Mon 16.15-18 in hall R2
• Design exercise: notified later
• Exam: 16.12.2015, (20.10.2015 for students from previous
years)
Execution
• Compulsory:
– Design exercise
– Exam
• Recommended and desirable:
– Attending lectures
– Solving exercies independently at home
• Course books:
– RIL 243-1-2007 (only available in
Finnish)
– Master Handbook of Acoustics,
Everest&Pohlman (a few sections, to be
notified later)
The scope of acoustics
[Lindsay 1964, muutettu]
[Lindsay`s wheel of acoustics,
1964, modified / Remes]
Brief history of acoustics...
”Acoustics is a science of the last thirty years.”
Physicist Dayton Miller 1931
History...
Creek. aκουειν = ”to hear”
• 6th century BC
Pythagoras investigates the relation between the length and pitch of
strings
• 325 BC
Aristotle writes about the production and reception of sound and
echoes
• 27 AD
Marcus Vitruvius Pollio: De Architectura, first instructions on the
acoustic design of theaters
• 800s 
Islamic culture produces new knowledge on sound-related phenomena
(e.g. hearing and speech production)
• 1500s
The effects of Renaissance cathedrals on music
History...
• Mid 1600s
Sound reflection and echoes are explained as analog to the
reflection of light, R. Boyle ja R. Hooke deduce that sound needs a
medium in order to propagate, G. Galilei investigates the vibration
of strings
• 1670`s
First purpose-built concert hall is finished in London
• 1700s
Commercialisation of music and theatre industry creates new social
and acoustical framework
• 1816
P. S. Laplace discovers the equation for calculating the speed of
sound (Newton attempted this before but did not get the right result)
History...
•
•
•
•
•
Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces
(background: growing need for auditoria and development of orchestral
music). C. Bullfinch, R. Mills and J. S. Russell develop methods for
improving speech intelligibility in rooms.
1850
Joseph Henry discovers the Precedence effect and evaluates that the
shape of the room does not explain alone the way it sound, but materials
have to be considered also
1860s
Hermann von Helmholtz investigates speech production, sense of hearing
and sound disturbance
1876
A. G. Bell invents the microphone (however, condensator microphone is not
invented until 1916)
1877
Lord Rayleigh: The Theory of Sound, the mathematical principles of sound
and vibration
History...
• End of 1800s
Wallace Clement Sabine hired to improve the acoustics of the
Fogg Art Museum in Harvard
 Sabine invents a method for measuring the reverberation time
of a room using an organ pipe and stopwatch
 Sabine equation for calculating the reverberation time
• 1895
W. C. Sabine as acoustical designer of the Boston Symphony Hall
• 1920
Efirst patented acoustical tile
• 1927
First anechoic chamber built (F. Watson)
History...
• 1930s
First sound level meter (P. Sabine)
• 1930s 
Suggestions for sound insulation regulations in several countries,
measurement of and methods to decrease traffic noise in large
cities
 acoustics becomes a tool for humans to control the environment
• 1943
The Finnish Ääniteknillinen yhditys (now Akustinen Seura /
Acoustical Society of Finland) is established
 the field of acoustical expertise in Finland expands, teaching
acoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technology
• Old field of science but significant effects not until the 20th century
• Acoustics has enabled, e.g.
–
–
–
–
Telephone, radio, recording and reproduction of sound, talking movies
Hearing protection in industrial labour
Privacy in residential buildings
The building of spaces which work according to desired function
• Sound plays an important role in how people experience and
perceive the surrounding environment
–
–
–
–
–
Hearing
Speech, communication
Music
Warning signals
Sound in nature
Acoustical design of buildings
” Akustinen suunnittelu on suoritettava samanaikaisesti
yleisen suunnittelutyön yhteydessä, jotta saadaan
estetyksi sellaiset ratkaisut, jotka estävät optimaalisten
akustisten tulosten saavuttamisen.”
Tekniikan lisensiaatti Eero Lampio 1962
The ”four-field” of acoustical design
Building
acoustics
Room
acoustics
Acoustical design
of buildings
(Architectural
acoustics)
Noise
control
Vibration
isolation
The ”four-field” of acoustical design
Room acoustics
• ”Good room acoustics
means that speech and
music is perceived as
beautiful, natural and
clear in every point of
the room.”
Engineer U. Varjo 1938
• The reflection,
attennuation and
propagation of sound in
a space
• Goal: sound (speech,
orchestra etc.) sounds
as is required by the
use of space
Building acoustics 1/3
• Transition of sound
between spaces via
structures
– Not only through the
separating structure, but
also as flanking
transmission and through
holes etc.
• 3 parts depending on the
nature of the sound
source:
– Airborne sound insulation
– Impact sound insulation
– Structure-borne sound
insulation
Building acoustics 2/3
• Sound insulation
45
40
35
30
25
20
15
10
Kipsilevy 2 x 13 mm (18 kg/m2)
Puu 50 mm (25 kg/m2)
5
Kevytbetoni 68 mm (27 kg/m2)
Taajuus [Hz]
3150
2000
1250
800
500
315
200
125
80
0
50
• Choosing the
construction type is
also acoustic design
50
R ' [dB]
– Between spaces
(airborne and impact)
– From inside to
outside and vice
versa
– Equipment noise
– Vibration
Rakenteiden
ilmaääneneristävyyksiä
Building acoustics 3/3
• Airborne sound (ilmaääni) is sound
produced in and propagated in air,
whereas structure-borne sound
(runkoääni) propagates in
structures
• Speech is airborne sound
• Sounds caused by walking or
dropping objects on the floor are
impact sound (askelääni)
• Piano produces airborne sound and
structure-borne sound through its
feet which are in contact with the
floor structure
• All technical equipment produce both
airborne and structure-borne sound
Noise control 1/2
• Outdoor noise sources:
road, railway and
airplane traffic
• Indoor noise sources:
machinery and service
equipment (talotekniikka)
• Goal: to diminish the
production and
propagation of noise
Kuva: Salter 1999
Noise control 2/2
• HVAC equipment
– outdoors
– indoors
• Traffic noise
– Road traffic
– Railway traffic
– Airplane traffic
• Machinery, industry
• Measurement of noise
emission
• Noise modelling
Vibration isolation 1/2
”Älköön kukaan… pitäkö
varastoa, tai käyttäkö
kiinteistöä niin, että
naapuri taikka muu…
kärsii siitä pysyväistä
kohtuutonta rasitusta,
kuten kipinöiden,
tuhkan, noen, savun,
lämmön, löyhkän,
kaasujen, höyryn,
tärinän, jyskeen taikka
muun sellaisen kautta.”
Laki eräistä naapuruussuhteista
1920
Vibration isolation 2/2
• All machinery in
contact with the
building frame vibrate
and produce sound
• Goal: to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Sähköjohto vapaasti riippuvana lenkkinä
Pallotasain
Pallotasain
Betonilaatta 250 mm
Tärinäneristimet
Betonimassa
Goals os acoustical design
• Suitability to intended use
– Suitability to speech / music
– Appropriate sound insulation
between spaces
• Healthiness
– Hearing loss
– Acoustic ergonomy
• Comfort
– Living spaces in noisy areas
– Connection between acoustics and
aesthetics
• (”wow-factor”)
– Concert halls etc.
Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit,
Helimäki Acoustics
Significance of acoustical design 1/3
•
The starting points of acoustic design:
1. Healthiness
2. Comfort
3. Use of space
•
Achieving good acoustical conditions in a building
requires that all the points are taken into consideration!
•
The need of acoustical design is not limited to
demanding spaces such as concert halls, but acoustical
design is needed in everyday buildings as well (when,
e.g., choosing the construction type of a soundinsulating structure in a school or residential building)
Significance of acoustical design 2/3
•
•
•
Sound constitutes a significant part of the human
sensory environment
Noise (”unwanted sound”) has significant physiological
anf psychological effects on humans
–
Research has been extensive from the beginning if the 20th
century
–
The effects of noise are not limited to loud noise (hearing
damage risk), but also a quiet sound can be perceived as noise
if it, for example, hinders concentration
Bad acoustics also has economic consequences...
Akustiikka 10/11
Significance of acoustical design 3/3
Investing in acoustics is worth it
• A space which does not function acoustically as required by
its use is a stranded investment, i.e. bad business!
• Improving the acoustical conditions in a finished building is
always expensive
–
–
–
–
–
–
Meetings
Measurements
Work of experts
Work spent by the user to solve the problem
Larger design costs
Larger building costs
• Savings earned during the use of the building
– The effects of acoustics on working conditions
– There is no need to do changes to a space which works as
intended!
Regulations and instruction in acoustics
• The National Building Code of Finland, Section C1-1998
• The National Building Code of Finland, Section D2-2010
• Asumisterveysohje (2003) by the Ministry of Social Affairs
and Health
• Government Decision on the Noise Level Guide Values
(993/1992)
• Acoustic Clasification of Spaces in Buildings, standard SFS
5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible – the sooner, the more demanding the project is!
Acoustics in the building project
Project planning phase (hankesuunnittelu)
• Sound insulation
– Appropriate level of sound insulation according to use of spaces
– Space program (tilaohjelma): positioning of noisy / quiet spaces
• Room acoustics
– Use of space  surface area, volume, shape, room acoustical
materials
• Control of HVAC noise
– Determine the permitted noise levels
– Space needs required by noise control measures (silencers etc.),
positioning of engine rooms and noisy machinery
• Control of traffic noise
– Noise surveys ( recommendations, e.g., for positioning of
buildings, estimate of the need for facade sound insulation
(ulkovaipan ääneneristys, UÄE)
– Vibration surveys
Acoustics in the building project
Preliminary design phase (luonnossuunnittelu)
• Sound insulation
– Definition of sound insulation target values
– Construction types of separating and flanking structures, sound insulation
requirements of doors, floor coverings
• Room acoustics
– Basic shape of speech and performance spaces, room acoustical requirements
as technical values (e.g., reverberation time)
– Amounts and types of room acoustical materials, furnishings and decoration
• Control of HVAC noise
– Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled, selection of sewer system
• Control of traffic noise
– More accurate noise survey (requirements for facade sound insulation, balcony
glazings, noise barriers), effects of vibration surveys
– Determination of construction types: exterior wall (US), roof (YP) (sufficient
sound insulation for a given use)
– Facade sound insulation survey (ulkovaipan ääneneristys, UÄE)
 Cost for the project
Acoustics in the building project
Implementation planning phase (toteutus-) 1/3
• Control of traffic noise
– FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase),
supplementations and/or correctiong to FSS if needed
– Final selection of noise barries Meluesteiden lopullinen valinta (in
collaboration with the architect)
• Sound insulation
– Presentation of the details of structural joints for the structural designer,
drawing of details if needed
– Supervision of structutal design so as to ensure that the sound insulation of
joints and building elements corresponds to set requirements
• Room acoustics
– Positioning of room acoustical materials in different spaces  to the
architect, approval of furnishings etc. selected by the interior designer
– Structural designer checks the possible effects of room acoustical materials
assigned to the surfaces US, YP etc. structures
Acoustics in the building project
Implementation planning phase (toteutus-) 2/3
• Control of HVAC noise
– HVAC designer presents the acoustical designer pressure drop
calculations, equipment lists, HVAC drawings and noise data on all
equipment, fans etc.
– Sound insulation of machine room structures, noise level caused by
HVAC equipment to inside spaces and outside, sound insulation
through ducts  determination of duct silencers
– Selection of vibration isolators for techical equipment and
implementation of vibration isolation (principles)
– Periaatepiirustukset and instructions of pass-throughs
(LÄPIVIENNIT) and sealings: ducts, electrical installations, heating
pipes etc., possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or
to an acoustical specification (työselitys), which is
distrubuted to all building contractors
Acoustics in the building project
Implementation planning phase (toteutus-) 3/3
• Training of construction workers if needed
– Why is something done?
– What is important from the acoustical viewpoint?
• Check the effects of possible changes to plans
– Construction types, details, changes occuring on the building
site
– Changes due to selection of HVAC equipment (typically affect
the design of silencers)
– Inspection of vibration isolators
• Site supervision and inspection visits in demanding
projects
• Control measurements
 Implementation according to plans
Sound as a physical phenomenon,
basic concepts of acoustics
”Akustiikassa on esitettävä suureita, joiden suuruudet ja
väliset suhteet vaihtelevat erittäin paljon. Tämän
johdosta on otettu käyttöön logaritminen asteikko, johon
meidän nyt on tutustuttava, ennen kuin voimme jatkaa.”
Yli-insinööri Paavo Arni 1949
What is sound?
• Changes in air pressure in relation to static air pressure
• In air sound propagates as longitudinal wave motion
Kuvat: Everest & Pohlman 2011
Sound pressure level (SPL)
• Sound pressure p = change in air pressure in relation to
static air pressure (ca. 100 kPa)
• Smallest detectable sound pressure: p0 = 20 μPa
• Sound pressure corresponding to treshold of pain: 20
Pa
• Sound pressure level [dB]:
p2
p
L p  10 lg 2  20 lg
p0
p0
Frequency and wavelength
• Frequency f [Hz] = number of
vibrations per time unit
• Normal hearing range: ca. 20 –
20000 Hz
• Relation between frequency and
wavelength:
c
c
f  

f
• c = speed of sound
(343 m/s in air, T = 20 °C)
Kuva: Hongisto 2011
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
”equal loudness contours”
(ISO 226)
Sensitivity of hearing to
different frequencies is
not constant!
 Must be considered
when, e.g., evaluating the
noise annoyance
Hearing
treshold
Frequency bands
Octave bands
120
100
Äänenpainetaso [dB]
80
60
40
20
0
16
31,5
63
125
250
500
1000
Oktaavikaistan keskitaajuus [Hz]
2000
4000
8000
16000
Terssikaistan keskitaajuus [Hz]
20000
16000
12500
10000
8000
6300
5000
4000
3150
2500
2000
1600
1250
1000
800
630
500
400
315
250
200
160
125
100
80
63
50
40
31,5
25
20
16
12,5
Äänenpainetaso [dB]
Frequency bands
One-third octave bands
120
100
80
60
40
20
0
A-weighting
120
100
80
40
20
-20
-40
-60
Painottamaton keskiäänitaso
A-painotettu keskiäänitaso
-80
Terssikaistan keskitaajuus [Hz]
A-painotus
20000
16000
12500
10000
8000
6300
5000
4000
3150
2500
2000
1600
1250
1000
800
630
500
400
315
250
200
160
125
100
80
63
50
40
31,5
25
20
16
0
12,5
Äänenpainetaso [dB]
60
A-weighting
Sound level
• Due to practical reasons the sound pressure level
measured in the whole frequency range using Aweighting is usually given as a single number
• This single number quantity is called sound level
(äänitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
• Some of the sound sources in built environment produce
steady and continuous noise (e.g. air conditioning), others act
intermittently and instantaneously
 both long-term equivalent (= average) and instantaneous
maximum sound level must be considered
• Equivalent sound level LA,eq,T [dB] (keskiäänitaso) is the
average sound level during the investigated time period T:
1
LA ,i / 10 
LA,eq,T  10 lg  Ti 10

T i

• Maximum sound level LA,max [dB] (enimmäisäänitaso) is the
instantaneous peak value of the sound level during the
investigated time period
Addition of sound levels
• Generally for two sound sources (Lp,1 ja Lp,2):

Lp ,tot  10  lg 10
L p ,1 /10
 10
L p , 2 /10

• For N sound sources:
 N L p ,n /10 
Lp ,tot  10  lg 10

 n 1

• The formulas apply to non-correlating sound sources,
i.e., when the phases of the sound waves are
independent of each other; this condition is true for all
every-day sound sources
Addition of sound levels
Addition of sound levels
• If the difference between sound levels exceeds 10 dB,
the louder sound practically determines the total sound
level!
[Figure: Hongisto 2011]
Sound power level (äänitehotaso)
• Sound power W [W] = the ability of a sound source to
produce sound
• Sound power corresponding to hearing treshold: W0 = 1 pW
• Sound power level LW [dB]:
W
LW  10 lg
W0
• Sound power or sound power level is not directly measurable
quantity, but it must be determined by calculation, e.g., from
the sound pressure level measured at a known distance from
the sound source
• Note: Sound power level is a property of the sound source
and does not depend on the environment!
Sound intensity level (intensiteettitaso)
• Sound intensity I [W/m2] = power per unit area
• Intensity corresponding to hearing treshold: 1 pW/m2
• Sound intensity level:
I
LI  10 lg
I0
• The relation between sound intensity and power:
W  SI
where S is surface area [m2]
Measurement of sound power level
• Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source:
LW  LI  10 lg S
äänilähde
mikrofoni
lattia/maa
Sound propagation and attenuation
Spherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva: Salter et. al 1999
Sound propagation and attenuation
Sound divergence in a free field
• Sound pressure level of a sound source at a given
distance from the source can be calculated from the
sound power level (in Finnish ”leviämisvaimennus”):
 r 2 
distance attenuation

L p  LW  10 lg
 k 
where Ω is solid angle (avaruuskulma) and k is
directivity factor (suuntakerroin) of the sound source
• When Ω = 4π (spherical wave) and k = 1, we get:


Lp  LW  10 lg 4r 2  LW  20 lg r  11
 in a spherical wave Lp decreases 6 dB, with
doubling of distance
Sound propagation and attenuation
Effect of location
• The effect of location of the source (i.e. solid angle Ω):
b)
Distance attenuation in spherical
wave
a)
c)
Spherical wave:
Distance x 2  Lp - 6 dB
Distance attenuation in cylidrical wave
b)
a)
c)
Cylindrical wave:
Distance x 2  Lp - 3 dB
Sound propagation and attenuation
Directivity factor
• Definition of directivity factor k: k  I

Ik
meaning: directivity factor at angle θ = sound intensity at
angle θ / average intensity of sound source radiated to
all directions
• Determining the directivity of a sound source is difficult,
thus directivity information of, e.g., HVAC equipment is
rarely available
 sound sources are typically treated as point sources
(k = 1, no directivity)
Sound absorption
• The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
• Sound absorption coefficient, α, is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 – W2:
W1
W1  W2

W1
α = 0...1
W2
Measurement of absorption coefficient
• Absorption coefficient is a
frequency-dependent
quantity
• Measured usually in onethird bands 100-5000 Hz in
a reverberation chamber
(ISO 354)
• Different single-number
descriptors can be
calculated from the
measurement results (e.g.,
Absorption Class, ISO
11654)
Sound absorption vs. sound insulation
Sound absorption vs. sound insulation
Reflection - transmission
• Reflection:
Wi  Wr

Wi
α = 0...1
– Large value: sound absorbed
– Small value: sound reflected
• Transmission:

Wt
Wi
τ = 0...1
– Large value: most of the sound energy penetrates the structure
– Small value: sound reflected
Sound absorption vs. sound insulation
Reflection - transmission
• Attenuation of sound hitting a
surface as a function of
absorption coefficient:
D  10 lg1   
• Attenuation of sound penetrating
the structure as a function of
transmission coefficient:
 Wi
1
R  10 lg   10 lg
 
 Wt



Reverberation time
• The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
• Measurement of reverberation time using the impulse
method:
Reverberation time
• Reverberation time is
calculated using the
Sabine equation:
V
T  0,16
A
• Other formulae also
exist
Reverberation time
Diffuse sound field
• Sabine equation assumes a diffuse sound field in the
room
• Diffuse sound field: equal sound pressure level at each
point in the room
– Condition is satisfied in cubic spaces with dimensions >> sound
wavelength and with hard sound reflecting surfaces
– Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
• Sabine equation can, however, be applied in most
spaces with sufficient accuracy
Sound absorption area
• Absorption area in Sabine equation A [m2] depends on
– Sound absoprtion coefficients of materials α
– Surface areas S of materials in the room
• Total sound absorption area:
n
A  1S1   2 S 2  ...   n S n   i Si
i 1
• Note: Aabsorption area and reverberation time are
frequency-dependent quantities!
Examples of reverberation time
Tila
Jälkikaiunta-aika T [s]
0,2 s…0,3 s
Äänitarkkaamo
0,3 s…0,8 s
Elokuvateatteri
0,5 s
Kalustettu makuuhuone
0,5 s…0,8 s
Hyvin suunniteltu luokkahuone
1,0 s…1,2 s
Teatteri, suuri auditorio
1,5 s
Kalustamaton makuuhuone
1,8 s
Tampere-talon iso sali
2 s…3s
Suuri aula, jossa ei vaimennusta
5s
Tampereen tuomiokirkko tyhjänä
9,5 s
Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
• The sound pressure level produced by a sound source
in a room can be calculated from the equation:
 A
L p  Lw  10 lg 
4
• The latter term is called room attenuation
(huonevaimennus)
• Equation only takes account of the sound reflected from
room surfaces and assumes a diffuse sound field
• Note:
– A > 4 m2  positive room attenuation (sound attenuates)
– A < 4 m2  negative room attenuation (sound amplified)
Room attenuation
• Room attenuation:
 A
10 lg 
4
The absorption area
and room attenuation
of a typical furnished
room:
10 m2  4 dB
Significance of room attenuation
• The sound level caused by a sound source depends
highly on the amount of room attenuation
 must be considered, e.g., in HVAC noise control!
Sound field in enclosed spaces
• Sound pressure level in an enclosed space:
4
 k
L p  LW  10 lg 2  
A
 r
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spaces
Reverberation radius
• Sound level in a room reaches a certain constant level a
few meters from the sound source
• This distance is called reverberation radius
(kaiuntasäde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal:
rk 
kA
4
Sound field in enclosed spaces
Puheen äänitaso L A [dB]
reverberation radius
80
70
60
DL2 saadaan jyrkkyydestä:
r1=2 m ja L1=53 dB,
r2=4 m ja L2=42 dB
DL2=11 dB
50
40
30
20
0.1
1
10
Etäisyys äänilähteeseen r [m]
Diffuusi huone, yhtälö (4.20), DL2=0 dB
Avotoimisto, huono vaimennus, DL2=5 dB
Avotoimisto, hyvä vaimennus, DL2=11 dB
Heijastukseton tila (tai ulkona)
100
Characteristics of human speech
normaali
dB
57,2
59,8
53,5
48,8
43,8
38,6
59,5
62,6
Hz
250
500
1k
2k
4k
8k
A
Lin
korotettu
dB
61,5
65,6
62,3
56,8
51,3
42,6
66,5
68,7
Suhteellinen äänitaso [dBA]
90
110100 4
120
2
130
0
140
-2
150
-4
160
-6
170
-8
180
-10
80 70
20
Taajuus [Hz]
0
250
500
1k
190
10
340
330
320
310
300
280290
270
40
350
20
pystysuunta
60
0
60
40
30
200
Äänitaso [dB]
80
Suhteellinen äänitaso [dBA]
90
110100 4
120
2
130
0
140
-2
150
-4
160
-6
170
-8
180
-10
50
190
210
220
230
240
250260
voimakas
dB
64,0
70,3
70,6
65,9
59,9
48,9
73,7
74,7
200
2k
4k
80 70
8k
60
50
40
30
20
10
0
350
340
210
330
220
320
vaakasuunta
230
310
240
300
250260
280290
270