Examining the difference between laboratory measurements and calculation results in impact sound insulation Mehmet Okay 1 Yildiz Technical University Yildiz, 34349 Besiktas/Istanbul, Turkey Mehmet Nuri Ilgurel 2 Yildiz Technical University Yildiz, 34349 Besiktas/Istanbul, Turkey Rahmi Guclu 3 Yildiz Technical University Yildiz, 34349 Besiktas/Istanbul, Turkey

ABSTRACT Architectural structures are designed and built to provide a comfortable living space to their users due to their function. One of the most important comfort expectations in buildings is acoustic comfort. Since the impact sound insulation between floors, which is one of the sub-headings of acoustic comfort, is evaluated together with the floor covering, resolving the discomfort caused by incomplete or incorrect evaluations during the design phase can be both more difficult and more costly during operation. In practice, it has been observed that there are differences between the laboratory measurements made according to the EN ISO 10140-3 standard and the calculations made according to the EN ISO 12354-2 standard for impact sound insulation. This difference can lead to an uncomfortable living space as the targeted acoustic performance cannot be achieved. This situation creates the need for a calculation model that gives more realistic results during the design phase. In this study, the variables that cause the difference between laboratory measurements and calculation results in impact sound insulation will be examined and improvement suggestions will be developed for the calculation of impact sound insulation according to the EN ISO 12354-2 standard.

1. INTRODUCTION

Architectural buildings should meet the comfort expectations of people in accordance with the rules of building physics and the limits drawn by the regulations, as well as the shelter and protection need of people. Due to factors such as population growth, climate change, and the development of technology, people's expectations from buildings are changing and/or going up. In building design,

1 okaymehmet92@gmail.com , mehmet.okay@std.yildiz.edu.tr

2 milgurel@yildiz.edu.tr

3 guclu@yildiz.edu.tr

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compliance with the rules of building physics is expected along with the expectations of economy, safety, aesthetics and functionality. Acoustic comfort, thermal comfort and visual comfort are evaluated as sub-headings of building physics. While the increase in high-rise buildings makes noise control crucial in buildings, volume acoustics is evaluated in order to provide a quality audi- tion in art buildings. Impact sound insulation, which is examined in this study, is evaluated as a sub-title of noise control. Since the measures for impact sound insulation should be evaluated together with the floor covering, it is important to apply correctly designed systems. It will be much more difficult to eliminate the discomfort caused by incomplete or incorrect designs during operation, additionally it will create undesirable cost and time losses. For this reason, this study was carried out in order to offer improvement suggestions in line with the findings in the impact sound insulation evaluation.

2. IMPACT SOUND LEVEL

Impact sound arises due to the impact on the building element. For this reason, to prevent discom- fort caused by impact, it is tried to minimize the effect of the force applied by the impact or the vibration on the structural element. The expectation of comfort may differ according to the purpose of use of the building and the type of building. Comfort conditions are achieved objectively and numerically from the regulations of the countries [countries]. In order to insulate the impact sound, floating floor application may be done or measures can be taken under floor covering like parquet and carpet, depending on the comfort expectations. Evaluations for impact sound insulation are made according to ASTM and ISO standards. ISO standards were taken into account in this study. Field measurements for impact sound insulation are made in accordance with EN ISO 16283-2, laboratory measurements are made in accordance with EN ISO 10140-3 and theoretical calculations are made in accordance with EN ISO 12354-2 standards [1].

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2.1. Calculation of Impact Sound Level Schematic transmission ways have been drawn (see Figure 1) and the following steps are followed for impact sound insulation level calculations according to EN ISO 12354-2;

Figure 1: Direct and Flanking Transmission [2] • Direct transmission (L n,Dd , dB) is calculated with Equation 1 [3],

𝐿 𝑛,𝐷𝑑 = 155 −ቆ30 ∗logሺ𝑚 ′ ሻ+ 10 ∗logሺ𝑇 𝑠 ሻ+ 10 ∗log ሺ σ ሻ+ 10 ∗log ሺ 𝑓

ሻቇ (1)

𝑓 𝑟𝑒𝑓

• Flanking transmission (L n,Df , dB) is calculated with Equation 2 [3],

𝐿 𝑛,𝐷𝑓 = 𝐿 𝑛,𝐷𝑑 −∆𝐿+ 𝑅 𝐷 − 𝑅 𝑓,𝑖

2 − ∆𝑅 𝑓 − 𝐷 𝑣,𝐷𝑓,𝑛 തതതതതതതതത −10 ∗log ඨ 𝑆 𝐷

(2)

𝑆 𝑓

• Total impact sound level is calculated with Equation 3 [3],

𝑛

𝐿 𝑛,𝐷𝑓,𝑗

𝐿 𝑛,𝐷𝑑

10 + ෍ 10

ቍ (3)

𝐿′ 𝑛 = 10 ∗log ቌ 1 0

10

𝑗=1

• Volume effect of the receiver room is calculated with Equation 4 [3],

𝐿′ 𝑛𝑇 = 𝐿′ 𝑛 −10 ∗log ቆ 𝐶 𝑠𝑎𝑏 𝑥 𝑉

ቇ (4)

𝐴 0 𝑥 𝑇 0

• All above calculations are made with frequency range of 50 Hz – 5000 Hz. All frequency results are weighted according to EN ISO 717-2 to a single impact sound level which is L’ nT,w (dB). [4]

2.2. Floating Floor Applications for Impact Sound Insulation As it is mentioned, to provide acoustically comfortable living spaces it is needed to prevent or to reduce impact transmission to the floor. In order to achieve required impact sound insulation level, it is needed to decide comfort conditions from regulations. Required impact sound insulation level is calculated with Equation 4, [3],

∆𝐿 𝑤 = 𝐿′ 𝑛𝑇,𝑤 [𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑] −𝐿′ 𝑛𝑇,𝑤 [𝑅𝑒𝑔𝑢𝑙𝑎𝑡𝑖𝑜𝑛] (5)

Previous studies have been showed that if the thickness of reinforced concrete floor is thin and comfort condition is high, floating floor should be applied (see Figure 2 and Figure 3) [2].

Concrete Floor Slab Thickness (cm) 15 16 17 18 19 20 21 22 23 24 2 5 26 27 2 8 29 3 0 31 3 2 3 3 3 4 3 5 3 6 3 7 3 8 39 40 A Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 46 dB] 31,1 30,3 29,5 28,7 28,0 27,3 26,6 25,9 25,3 24,7 24,1 23,5 22,9 22,4 21,9 21,4 20,9 20,4 19,9 19,5 19,0 18,6 18,1 17,7 17,3 16,9

Medium Level

Noise (MN) High Level Noise

B Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 50 dB] 27,1 26,3 25,5 24,7 24,0 23,3 22,6 21,9 21,3 20,7 20,1 19,5 18,9 18,4 17,9 17,4 16,9 16,4 15,9 15,5 15,0 14,6 14,1 13,7 13,3 12,9

C Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 54 dB] 23,1 22,3 21,5 20,7 20,0 19,3 18,6 17,9 17,3 16,7 16,1 15,5 14,9 14,4 13,9 13,4 12,9 12,4 11,9 11,5 11,0 10,6 10,1 9,7 9,3 8,9

A Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 40 dB] 37,1 36,3 35,5 34,7 34,0 33,3 32,6 31,9 31,3 30,7 30,1 29,5 28,9 28,4 27,9 27,4 26,9 26,4 25,9 25,5 25,0 24,6 24,1 23,7 23,3 22,9

B Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 44 dB] 33,1 32,3 31,5 30,7 30,0 29,3 28,6 27,9 27,3 26,7 26,1 25,5 24,9 24,4 23,9 23,4 22,9 22,4 21,9 21,5 21,0 20,6 20,1 19,7 19,3 18,9

(HN)

C Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 48 dB] 29,1 28,3 27,5 26,7 26,0 25,3 24,6 23,9 23,3 22,7 22,1 21,5 20,9 20,4 19,9 19,4 18,9 18,4 17,9 17,5 17,0 16,6 16,1 15,7 15,3 14,9

Figure 2: Impact sound insulation (∆Lw) requirements according to Turkish Regulations [2]

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Concrete Floor Slab Thickness (cm) 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 A Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 46 dB] B Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 50 dB] C Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 54 dB] A Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 40 dB] B Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 44 dB] C Class Acoustic Performance ∆Lw (dB) [L'nT,w ≤ 48 dB]

Medium Level

Floating Floor

Floor Covering

Noise (MN) High Level Noise

Floating Floor Floor Covering

Floating Floor Floor Covering

Floating Floor

(HN)

Floating Floor

Floating Floor Floor Covering

Figure 3: Usage area of floating floor according to Turkish Regulations [2] 3. IMPACT SOUND INSULATION

Impact sound insulation calculations for floating floor are made with accordance to EN ISO 12354- 2 standards with Equation 6 and Equation 7 [3];

𝑓 0 = 160 ∗ ඨ 𝑠′

𝑚′ (6)

∆𝐿 𝑤 = 30 ∗ log 𝑓

(7)

𝑓 0

s’ = Dynamic stiffness of elastic impact sound insulation layer (MN/m 3 ) m’ = Mass per unit are of floating floor (kg/m 2 ) f 0 = Natural frequency of the system (Hz) f = Center frequency in Hertz of the one-third or octave band (Hz) ∆L w = Impact sound insulation level (dB) As it is seen that in Equation 6, impact sound insulation performance of floating floor is related to dynamic stiffness of elastic impact sound insulation layer which is used under floating floor and mass per unit area.

However, some studies have shown that there are notable differences between laboratory measurements and calculations [5]. It will be examined that parameters which affect impact sound insulation performance in next parts.

3.1. Dynamic Stiffness Dynamic stiffness is the ratio of dynamic force to dynamic displacement. It is measured according to EN 29052-1 standards. Due to its measuring procedure which is that tests are done under 8kg and 20cm x 20cm steel plate, it is being assumed that dynamic stiffness is a constant value [6]. However, some studies have shown that dynamic stiffness of an elastic material is changing with the mass [7].

As it seen from Table 1, when dynamic stiffness is obtained by using Equation 6 and Equation 7 from the laboratory measurement results of some products, it has been observed that there are differences between the measured dynamic stiffness of the products and the calculated dynamic

stiffness [5].

Table 1: Measured and calculated dynamic stiffness of different materials [5]

Obtained from the Meas- urement Result According

Mass Per Unit Area of

Declared Dynamic

ΔLw (EN ISO 10140-3)

Stiffness

to EN ISO 10140-3, Using Equation 6 and Equation 7

Product

the Floating

s' (EN 29052-1)

Floor

s' (EN ISO 12354-2)

A 90 kg/m² 26 dB <18 MN/m³ 26,4 MN/m³

110 kg/m² 28 dB 23,7 MN/m³

B 60 kg/m² 19 dB <70 MN/m³ 51,5 MN/m³

90 kg/m² 20 dB 66,2 MN/m³

C 90 kg/m² 32 dB <7 MN/m³ 10,5 MN/m³

150 kg/m² 35 dB 11,0 MN/m³

D 90 kg/m² 25 dB <18 MN/m³ 30,7 MN/m³

150 kg/m² 30 dB 23,8 MN/m³

E 150 kg/m² 21 dB - MN/m³ 94,6 MN/m³

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220 kg/m² 22,4 dB 100,6 MN/m³

3.2. Creep Deflection

Every material which are used under floating floor have a creep deflection by time. Creep deflection changes the materials thickness and elasticity, and it is measured according to EN 1606 standards. According to EN ISO 10140-3 standards, laboratory measurements are generally completed three days after the floating floor is placed. However, some studies have been showed that creep deflection affects the dynamic stiffness of the material at a level that cannot be ignored (see Figure 4) [8].

Figure 4: A measurement for dynamic stiffness changing by time [8]

EVA-59-E -=-500N —-250N —-80N —-40N 100 200 300 400 500 Day

3.3. Dimensions of Floating Floor

It has been assumed in current standards, measured dynamic stiffness according to EN 29052-1 is independent from the dimensions of floating floor. Contrary to standards a study has been showed that impact sound insulation performance of a floating floor is changing with the dimensions of floating floor (see Figure 5) [9]. It is assumed that the deflection of floating concrete which is made by the moment diagram of floating floor affects the deflection of elastic layer under floating floor and dynamic stiffness is changing.

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45 a papipasg ag eRxanxegengvre ‘ap “IV Jana} aunssaud punos spedut ul uonanpas paysion,

Figure 5: Dependence between impact sound insulation performance and dimensions of floating floor [9]

3.4. Damping Ratio

Impact sound insulation is basically vibration isolation of single degree of freedom system as seen in Figure 6. The main idea is that preventing force transmission from floating floor to basic floor.

MASS or) 2 Ky 2 SPRING TTT,

Figure 6: Single Degree of freedom vibrating systems [10]

Although floating floor as mass-spring system has a damping, it is assumed that in current equa- tions the system is not damped. There is no other material as a damper in the system as seen in Fig- ure 6, but elastic insulation material has a damping capacity.

Some studies have been showed that damping ratio of the insulation material affects impact sound insulation performance [11].

y ws "@ SPRING DAMPER Ke Ry VT

Figure 6: Comparison between current calculation model and transmissibility model which includes damping ratio [12]

4. CONCLUSIONS

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To provide comfortable living places, sound insulation is one of most crucial topics. Because its structural effect in high-rise buildings, impact and vibration isolation must be considered according to standards and regulations. To prevent force transmission to the floor and provide impact sound insulation, mostly floating floor applications are needed. In order to eliminate the inconveniences to be experienced due to the wrong design of the floating floor system, it will cause reconstruction of the living area and the floating floor will be broken and rebuilt. This will create unforeseen time and cost losses. That is why the floating floor system should be designed correctly. However, studies have been showed that calculation and measurement results of impact sound insulation may be different noteworthily. Currently, mass per unit area of the floating floor and the dynamic stiffness which is measured according to EN 29052-1 are needed for calculation of impact sound insulation performance. On the other hand, as a result of this study, the following improvement suggestions have been made to ensure the impact sound insulation calculation result match the measurement results: • Because of creep deflection effect, dynamic stiffness of impact sound insulation material should be measured 21 days after the system has been prepared. (EN 29052-1) • Change of mass per unit area of floating floor is causing the change of dynamic stiffness of elastic layer. That is why, dynamic stiffness measurements should be made up with variable masses such as 4kg, 6kg, 8kg, 10kg steel plates. (EN 29052-1) • Concrete layer of floating floor tends to be deflected because of its moment diagram. When dimensions of floating floor change, deflection capacity of floating floor changes and therefore impact sound insulation performance changes. That is why, a new calculation model which includes dimensions of floating floor is needed. (EN ISO 12354-2) • Elastic materials which are using under floating floor have a damping capacity. This damping ratio affects impact sound insulation performance for each frequency. So, damping ratio should be included in improved calculation model. (EN ISO 12354-2)

Insulation ffectvess 4 beeicoseuses ta Normalized frequeny ffs

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