LECTURE 6, part 1 Traffic noise

Transcription

1 Rak Building Physics Design 2 ACOUSTICAL DESIGN Autumn 2015 LECTURE 6, part 1 Traffic noise Matias Remes, M.Sc. FISE A acoustics

2 Traffic noise and land use Tämän päivän melusta näyttää tulevan vaikea yhteiskunnallinen probleema, jonka merkityksestä ei kaikilla ihmisillä ole edes mielikuvaa. Melu ei ole tämän päivän tuotetta, sillä jo sata vuotta sitten oli huolestuneita ihmisiä, jotka kirjoittivat melusta ja hälystä. Mutta heidän päiviensä rattaiden kolinasta mukulakivikadulla on suuri askel nykypäivän liikennekohinaan. Tekniikan lisensiaatti Eero Lampio 1962

3 Traffic noise Noise sources Road traffic Railway traffic Air traffic Measurement of noise immision Noise modelling

4 Sound sources Road traffic noise Of the three noise sources road traffic constitutes the most significant environmental problem In the greater Helsinki area alone the amount people subjected to noise levels exceeding the guideline value of daytime equivalent noise level 55 dba is over The most significant sound sources are engine noises and tire noise, additionally noise is caused by air friction, force transmission, vibration of the hull and the possible noisy equipment on the vehicle Noise mainly comprises of engine noise when speed is Passenger vehicles: v < 40 km/h Heavy vehicles: v < 60 km/h The significance of tire noise increases with increasing speed At high speeds (v > 120 km/h) also flow noise due to air friction occurs

5 Sound sources Road traffic noise Road traffic noise is by nature even; the variation in sound level near the road is small Factors affecting noise attenuation ( rules of thumb ): Distance to road (distance 2x SPL decreases 3 db) Traffic amount (amount halves SPL decreases 3 db) Traffic speed (decrease from 100 km/h 80 km/h causes a decrease in SPL of 2 db) Terrain (in an area with soft terrain / ground surface SPL can be several decibels lower than in, e.g., in a city where sound is reflected from the walls of buildings and asphalt) Road surface (with porous silent road covering materials SPL can decrease > 3 db)

6 Sound sources Railway traffic noise ~ people are estimated to live in an area with daytime equivalent noise level caused by railway traffic exceeding the guideline of 55 dba Railway traffic noise is more instantaneous than road traffic noise (disturbance caused by train pass-bys with short duration) Noise is broad band and is caused mainly by the connection of the train wheels to the tracks Trains also cause structure borne noise and vibration depending on the terrain and foundation type of the tracks

7 Sound sources Spectrum of road and railway traffic noise

8 Sound sources Combined effect of road and railway traffic noise Railway traffic noise Road traffic noise Combined noise

9 Sound sources Air traffic noise Air traffic noise level is stated as day-evening-night noise level L DEN [db] Sound level difference required in detail plan (asemakaava) is based on L DEN -values In Finland new buildings should not be situated in areas with L DEN > 60 db The total number of people subjected to air traffic noise in Finland has decreased due to development of more silent aeroplanes, nevertheless air traffic noise constitutes a problem in areas near airports

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11 Sound sources Air traffic noise Connection between air traffic zones m1-3, corresponding L DEN values and sound level difference in Vantaa

12 Noise guidelines Council of State decree The Council of State decree (Valtioneuvoston päätös) VnP 993/1992 defines the highest permitted noise levels inside dwellings and in outdoor activity areas Inside dwellings: Day, between 7-22: LA,eq 35 db Night, between 22-7: LA,eq 30 db Outdoor activity areas and balconies: Day, between 7-22: LA,eq 55 db Night, existing dwelling areas, between 22-7: LA,eq 50 db Night, new areas, between 22-7: LA,eq 45 db

13 Noise guidelines Noise, health impairment and comfort Guidelines of equivalent noise level given in VnP 993/1992 are based on health effects of noise: Difficulties in falling asleep due to noise Waking up in the night due to noise disturbances In many cases single noise events are perceived as more disturbing than average noise; e.g. pass-bys of vehicles or trains causing a single noise peak Even though the guideline values (which are based on average noise level) were fulfilled, traffic noise can be heard and noise may cause disturbance

14 Control of traffic noise Prevention Land use design Traffic arrangements Safety distances to noise sources Positioning of building masses

15 Control of traffic noise Example of noise spreading

16 Control of traffic noise Noise barriers z D 10log101 20

17 Control of traffic noise Noise barriers Note: noise barrier only has effect near the ground surface!

18 Sound insulation of envelope (ulkokuori) Determination of the detail plan regulation Without reflection from the facade 70 db Permitted sound level inside 35 db 70 db Equivalent noise level outside without facade reflection 70 db Permitted equivalent noise level inside 35 db = Detail plan regulation (asemakaavamääräys) ΔL A,vaad 35 db

19 Sound insulation of the envelope Detail plan regulation Regulations given in the detail plan are based on the permitted noise levels inside a dwelling given in VnP 993/1992 Fulfilling the guideline values does not necessary guarantee dwelling comfort because the values are based on average noise level Standard SFS 5907 enables better acoustical conditions than required by VnP 993/1992 Class C: same values as in VnP 993/1992 Class B: 5 db lower equivalent noise level inside dwelling than required in VnP 993/1992 Class A: 10 db lower

20 Sound insulation of the envelope Calculation methods Requirement concerning the sound insulation of the envelope is stated in the detail plan as a sound level difference DL A Weighted sound reduction index of a facade or roof structure cannot be directly compared to the planning regulation, because the sound level difference is not the same thing as sound reduction index! A method is needed to calculate the sound insulation of the envelope There are no official regulations of what method should be used Two methods are used in Finland Environment guide 108/2003 method Sound level difference method (äänitasoeromenetelmä)

21 Sound insulation of the envelope Environment guide method The sound insulation requirement of the envelope of the investigated room is given by: R DL K 7 tr, vaad A 1 where ΔL A is the planning regulation and K 1 is a correction factor depending the surface areas of the envelope and the floor area of the investigated room:

22 Sound insulation of the envelope Environment guide method The method uses only weighted sound reduction indexes agains traffic noise (R A,tr = R w +C tr ) no matter what the noise source is Requirements for different parts of the envelope are given by: Exterior wall: R A tr, US R Roof: R A R, tr, vaad, tr, YP tr, vaad 5 3 Doors and windows: R A, tr Rtr, vaad K2

23 Sound insulation of the envelope Sound level difference method Sound level transmitted inside the room through a single building element of the envelope, L s, depends on the noise level outside (L U ), the sound reduction index of the element and the relation of the area of the element S i to floor area S H : L S L U i R w Ctr 7 10lg SH S... from which the sound level difference corresponding to a single building element can be solved: DL A, i L U L S i R w Ctr 7 10lg SH S

24 Sound insulation of the envelope Sound level difference method Sound level difference is calculated separately for each building element, DL A,i The total sound level difference of the envelope is given by: 1 DL A, kok 10lg n DL A, i /10 10 i1 In buildings the sound insulation of windows and doors which can be opened is not as good as in the laboratory (where the values have been measured); this is taken into account by decreasing the laboratory values in the calculation by 3 db

25 Sound insulation of the envelope Method comparison Both methods take account of the areas of building element in the envelope, floor area of the investigated room and the sound insulation values of all structures (exterior wall, roof, windos, doors, fresh-air vents), but Environment guide 108/2003 method Does not allow investigation of how the sound insulation of different building elements affects the sound level difference of the envelope Can lead to sound insulation requirements for windows and doors which are not possible to fulfill with any commonly available products on the market Sound level difference method Enables investigation of the sound level transmitted inside the room through a single building element Building element with weak sound insulation (e.g. window) can be compensated with a better sound insulating exterior wall, compensation is possible within a few decibels which can be significant to the total sound level difference of the envelope

26 Sound insulation of the envelope Measurement Measurement methods presented in standard ISO The are no regulations on which method should be used The main issue is that the method should produce a value which can be directly compared to the sound level difference given in the detail plan A measurement method in which this is the case is the measurement of the normalised level difference of the facade: A Dls, 2m, n L1,2 m L2 10lg A0 where L 1,2m is SPL produced by a loudspeaker measured at an 2m distance from the facade, L 2 is the SPL measured inside the receiving room, A is the absorption area of the receiving room and the normalising factor is A 0 = 10 m2

27 Sound insulation of the envelope Measurement D ls,2m,n is measured in one-third octave bands; the corresponding single-number value is D ls,2m,n,w Sound hitting the facade is reflected from it, causing the sound level in front of the facade to increase by about 3 db The reflection is directed away from the building This must be taken into account by subtracting 3 db from the measurement result The sum of sound level difference D ls,2m,n and spectrum adaptation term C tr subtracted by 3 db corresponds to the sound level difference of the planning regulation The measured sound level difference must, thus, be equal to or higher than the planning regulation: DL D C 3dB DL A, mit ls,2m, n, w tr If the planning regulation applies to railway of air traffic noise, the spectrum adaptation term C is used A

28 Sound insulation of the envelope Combined effect of building elements US: db db m 2 2 I: I: db db 22 m 2 2 US: db db m 2 2 I: I: db db 22 m 2 2 Through exterior wall 5 % Through window 95 % Through exterior wall 60 % Through window 40 %

29 Sound insulation of the envelope Effect of exterior wall on windows Floor area of room 12 m 2 Area of exterior wall 10 m 2 Area of window 2 m 2 Sound level difference required in detail plan 35 db Exterior wall Requirement for window R w + C tr R w + C tr

30 Sound insulation of exterior walls Concrete sandwich elements Ilmaääneneristävyys R [db] Exterior envelope 20 mm: Rw+Ctr = 48 db Exterior envelope 40 mm: Rw+Ctr = 49 db Exterior envelope 60 mm: Rw+Ctr = 49 db Keskitaajuus [Hz] Ulkokuori 20 mm Ulkokuori 40 mm Ulkokuori 60 mm

31 Sound insulation of exterior walls Inner envelope and thin rendering Ilmaääneneristävyys R [db] Paroc FAL1 150mm: Rw+Ctr = 39 db Paroc FAS4 160mm: Rw+Ctr = 41 db Isover FL 200mm: Rw+Ctr = 40 db Keskitaajuus [Hz] Jäykkä mineraalivilla ja ohutrappaus 10 mm 4000

32 Sound insulation of exterior walls Inner envelope and thin rendering Betonien sisäkuori [mm] eriste paksuus + tyyppi Rappaus [mm] R w (C, C tr ) [db] 150 mm 160 mm EPS 10 mm 52 (-3,-7) db 150 mm 160 mm EPS 25 mm 54 (-4,-9) db 150 mm 160 mm FAL1 10 mm 53 (-2,-5) db 150 mm 160 mm FAS4 25 mm 56 (0,-4) db 150 mm 250 mm EPS 10 mm 52 (-3,-8) db 150 mm 250 mm EPS 25 mm 54 (-4,-9) db 150 mm 250 mm FAL1 10 mm 53 (-2,-6) db 150 mm 250 mm FAS4 25 mm 58 (-1,-5) db 150 mm 450 mm EPS 10 mm 53 (-3,-8) db 150 mm 450 mm EPS 25 mm 56 (-1,-5) db 150 mm 450 mm FAL1 10 mm 54 (-3,-8) db 150 mm 450 mm FAS4 25 mm 59 (-1,-4) db

33 Sound insulation of exterior walls Inner envelope, studding, plate Ilmaääneneristävyys R [db] R w +C tr > 50 db Keskitaajuus [Hz] Rankarakenne ja tuulensuojakipsilevy 9 mm

34 Exterior walls with thin rendering Effect on sound insulation of the envelope Example: requirement ΔL A = 35 db US: 55 db 10 m 2 I: 37 db 2 m 2 US: 42 db 10 m 2 I: 37 db 2 m 2 Before renovation: US = concrete sandwich element ΔL A = 35 db After renovation: US = concrete inner envelope + insulation + thin rendering ΔL A = 32 db

35 Window renovations Effect on sound insulation of the envelope In window renovations: Windows are changed Often air conditioning is improved by installing freshair vents (korvausilmaventtiili) into the windows In noise sensitive areas, where there is a regulation for the sound insulation of the envelope, the effect of the renovations must be checked Fresh-air vents can deteriorate sound insulation Choosing the right type of vent Choosing the right type of window

36 Window renovations Effect on sound insulation of the envelope Example: requirement ΔL A = 35 db US: US: db db mm 2 2 I: I: db db 2 2 mm 2 2 US: US: db db mm 2 2 I: I: db db 2 2 mm 2 2 V:37 db db 1 1 mm 2 2 Before renovation: US = concrete sandwich element No fresh-air vents ΔL A = 35 db After renovation: US = concrete sandwich element Fresh-air vent added ΔL A = 33 db

37 Ventilation of the roof Effect on sound insulation of the envelope In air traffic noise areas the ventilation of the roof structure must be done so that sound leak via the ventilation channel does not deteriorate sound insulation Sound attenuating ventilation channel