acoustics i: building acoustics - people.ee.ethz.chisistaff/courses/ak1/... · building acoustics...

Building acoustics

introduction

airborne soundinsulation

single walls

double walls

standard soundpressure leveldifference

impact soundinsulation

SIA 181

construction hints

movie Cremer /Frobe

back

Acoustics I:building acoustics

Kurt Heutschi2013-01-25

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

introduction

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

introduction

I building acoustics → noise abatement in buildings(suppression of noise from neighbors)

I annoying sound is radiated by walls or ceilings

I excitation of these surfaces:I airborne sound sources such as e.g. voices,

loudspeakersI structure borne sound → vibration sources such as

e.g. footsteps

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

introduction

I material properties regarding suppression of airbornesound transmission → airborne sound insulation

I material properties regarding suppression ofstructure borne sound transmission → impact soundinsulation

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

airborne sound insulation

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

airborne sound insulationexperiment:

I airborne sound insulation: capability of a structureto suppress the transmission of sound that wasexcited by airborne sound

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back


I sound insulation index R (independent of the area!):

R = 10 log

(P1

P2

)[dB]

whereP1: incident sound power on the sender sideP2: sound power that is radiated by the rear side of thestructure

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back


I measurement of R :

P1 =

p21

ρc

4S

p1: sound pressure in sender roomS : area of the structure under consideration

P2 =

p22

ρc

4A2

p2: sound pressure in the receiving roomA2: total absorption in the receiving room = 0.16V2/T2

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back


from above follows:

R = 10 logp2

1

p22

+ 10 logS

A2

and finally:

R = L1 − L2 + 10 log

(S

A2

)[dB]

with:L1: average sound pressure level in the sender room (inthird octaves)L2: average sound pressure level in the receiving room (inthird octaves)

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back


I sound insulation index R is frequency dependent

I weighting of the frequency response with areference curve → single value: rated soundinsulation index Rw

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

sound insulation of singlewalls

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

sound insulation of single walls

I for plates, R depends on:I area specific mass m′′

I thicknessI density

I modulus of elasticityI frequency

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

sound insulation of single wallstypical frequency dependency of R :

region A mass law: R = 20 log(f ·m′′)− 47 [dB]

region B coincidence collapse f(φ):λbending:wave:plate = λprojection:air:borne:sound:wave

region C above coincidence, increase about 25dB/decade

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

sound insulation of doublewalls

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

sound insulation of double walls

I construction:I wall 1 + spacing (usually air) + wall 2I assumption of piston movement of walls: mass +

spring + mass

I → resonance leads to a collapse of sound insulation

I above resonance massive increase of soundinsulation with frequency

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

standard sound pressurelevel difference

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

standard sound pressure level difference

I disturbance relative to a noisy neighbor depends onI sound insulation index R of the structural elementsI common area F of the structural elementsI absorption, respectively reverberation of the

receiving room → normalized to 0.5 s

I → Standard sound pressure level difference DnT

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

standard sound pressure level difference

it can be found:

DnT = R + 10 log

(V

F

)− 4.9

with:V : room volume of the receiving room [m3]F : common area

I rated sound insulation index Rw → rated standardsound pressure level difference DnT ,w

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

impact sound insulation

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back


I excitation by hammers → standardized tappingmachine

I hammers of specified weightI specified falling heightI specified excitation frequency

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back


I measurement of average sound pressure level Li inthird octaves in the receiver room

I calculation of standard impact sound level Ln inthird octaves: total absorption of 10 m2 in thereceiving room is assumed

Ln = Li − 10 log

(10Ti

0.163V

)where:V : volume of the receiving room [m3]Ti : reverberation time in the receiving room in thirdoctaves

I translation into single value Ln,w analogous tosound insulation index by using a reference curve.

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

Swiss standard SIA 181

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

SIA 181: Noise protection in buildings

I SIA 181: defines building acoustical requirementsaccording to state of the art in building technology

I noise protection defined for two classes:I minimal requirements

I have to be fulfilled alwaysI elevated requirements

I have to be applied for single family houses thatare built together

I may be applied in other situations withagreement by contract

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back


I requirements defined as limiting values forI sound pressure level differences for

I exterior airborne soundI interior airborne sound

I impact sound

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back


I two dimensional scheme of limiting values:I first dimension: intensity of the sourceI second dimension: degree of sensitivity of the

inhabitants for a certain usage of the room

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

construction hints for goodbuilding acoustical

conditions

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

construction hints for good building

acoustical conditions

arrangement of rooms:

I suitable arrangement of rooms may help to avoidnoise problems

I good strategy: no rooms with different usage nextto each other (horizontally and vertically)

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back



doors and windows:

I typical maximum sound insulation of doors andwindows: 35 to 40 dB

I usually significantly weaker than walls

I for elevated requirements special constructions haveto be used

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back



leakage:

I already small openings (cracks) reduce soundinsulation between adjacent rooms drastically

I typical leakage elements: lead-throughs for cables orventilation ducts

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back



floating floors:

I bad idea to put walls directly on concrete floor →high structure borne sound transmission

I remedy: floating floors:I put layer of low stiffness on the concrete floorI floating top cover without contact to walls

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

movie Cremer / Frobe

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

movie Cremer / Frobe

Lehrfilm Cremer Frobe - Teil 1Lehrfilm Cremer Frobe - Teil 2

Building acoustics

introduction


single walls

double walls



SIA 181

construction hints

movie Cremer /Frobe

back

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acoustics i: building acoustics - people.ee.ethz.chisistaff/courses/ak1/... · building acoustics...

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