Reduction of transmitted impact sound of dry-type floating floor due to differences in impact force characteristics Ryuta Tomita 1 Nihon University 1-8-14, Kanda, Surugadai, Chiyoda-ku, Tokyo 101-8308, JAPAN

ABSTRACT In Japan, JIS A 1418-2:2019 specifies the car-tire with impact force characteristics (1) and the rub- ber ball with impact force characteristics (2) as standard heavy impact sources. It has also been reported that the reduction of transmitted impact sound differs depending on the impact sources of the car-tire and the rubber ball. It has been reported that one of the reasons for different reduction of transmitted impact sound is excessive the car-tire impact force, and a tendency for a nonlinear response to impact force for a dry-type floating floor. In this study, an experimental examination is conducted to interconvert the reduction of transmitted impact sound of the car-tire and the rubber ball. This manuscript discusses the reduction of transmitted impact sound due to the change in impact force by varying the drop height of the car-tire and the rubber ball. The results suggest that the difference in reduction of transmitted impact sound between the car-tire and the rubber ball cannot be explained only by nonlinearity due to the impact force for a dry-type floating floor.

1. INTRODUCTION

JIS A 1418-2:2019 [1] specifies the car-tire source with impact force characteristics (1) and the rub- ber ball source with impact force characteristics (2) as standard heavy-weight impact sources. In ad- dition, JIS A 1440-2:2007 [2] specifies the measurement method of the reduction of transmitted heavy- weight floor impact sound level. It has also been reported that the reduction of transmitted heavy- weight floor impact sound level differs depending on the impact sources of the car-tire and the rubber ball [3] .

Also, it has been reported that one of the reasons for different reductions of transmitted heavy- weight floor impact sound level is excessive the car-tire impact force, and a tendency for a nonlinear response to impact force for a dry-type floating floor.

In this study, an experimental investigation is conducted to interconvert the reduction of transmit- ted heavy-weight floor impact sound level of the car-tire and the rubber ball. In a previous report [4] , the height of the car-tire was lowered to make it slightly equal to the impact force of the rubber ball. As a result, it was clarified that only the excessive impact force did not affect the reduction of trans- mitted heavy-weight floor impact sound level. In addition, a method of converting the reduction of transmitted heavy-weight floor impact sound level of the rubber ball source into the reduction of the car-tire source has been proposed.

In this report, we examined another dry-type floating floor. In addition, the actual measurement value is compared with the result of converting the reduction of transmitted heavy-weight floor im- pact sound level of the car-tire source into the reduction of the rubber ball.

1 tomita.ryuta@nihon-u.ac.jp

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2. EXPERIMENTAL METHODS

2.1. Test Facility

The reduction of transmitted heavy-weight floor impact sound level was measured at a laboratory (Japan Testing Center for Construction Materials) in the wall-type reinforced concrete laboratory. Figure 1 shows the floor plan of the laboratory. The measurements were performed on a 200 mm slab.

S1

S4

S3

2,800

2,800

S2

S5

3,600 3,600

Frame

Sound source room (200mm slab) Sound source room (150mm slab)

L4,200cm

L1,140cm

L3,180cm

L5,100cm

L2,120cm

Sound receiving room (200 mm slab) Sound receiving room (150 mm slab)

Figure 1: Plan view of sound source room and sound receiving room.

2.2. Overview of Dry-type Floating Floor

The specifications of the dry-type floating floor used in the experiment are as shown in Figure 2.

Flooring 12mm

Flooring 12mm

Baseboard 35×9

Particle board 20mm

Particle board 20mm

98 20 12

98 20 12

Anti- vibration rubber

Anti- vibration rubber

25

20

Figure 2: Cross section of floating floor system (Left: General part, Right: End).

φ35

φ31

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2.3. Measurement method

The measurement of the reduction of transmitted heavy-weight floor impact sound level was per- formed in accordance with JIS A 1440-2:2007 [5] . The car-tire source with JIS A 1418-2:2019 [1] impact force characteristics (1) and the rubber ball source with JIS A 1418-2:2019 impact force characteristics (2) were used for excitation. Six vibration patterns were used: the bang machine, the 40 cm and 20 cm tire freefall, and the 100 cm, 50 cm, and 25 cm rubber ball freefall. In other words, the drop height was varied about twice.

An impact source was used to excite the five points shown in Figure 1. The five sound receiving points are shown in Figure 1. The reduction of transmitted heavy-weight floor impact sound level was calculated by subtracting the floor impact sound level of the dry-type floating floor from that of the bare concrete slab surface.

3. EXPERIMENTAL RESULTS AND DISCUSSION

3.1. Measurement Results of Concrete Slab Bare Surface

Figure 3 shows the results of the floor impact sound pressure level of the bare concrete slab sur- face. It was confirmed that the floor impact sound pressure level also decreased when the drop height of the car-tire and the rubber ball source decreased by approximately 1/2. The amount of re- duction was 2 to 7 dB with some variations in the 63 to 500 Hz band.

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Tire_Concrete slab_40cm

Tire_Concrete slab_Bang

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Tire_Concrete slab_20cm

Ball_Concrete slab_100cm

Ball_Concrete slab_50cm

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Floor impact sound pressure level (dB)

Floor impact sound pressure level (dB)

Ball_Concrete slab_25cm

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63 125 250 500 1000 2000 4000

63 125 250 500 1000 2000 4000

Octave band center frequency (Hz)

Octave band center frequency (Hz)

Figure 3: Floor impact sound pressure level of concrete slab.

3.2. Measurement Results of Reduction of Transmitted Floor Impact Sound Pressure Level

Figure 4 shows the reduction of transmitted heavy-weight floor impact sound level for the dry- type floating floor. For the dry-type floating floor in Figure 4, the characteristics of the rubber ball source were similar up to the 500 Hz band, regardless of the change in drop height. On the other hand, it can be seen that at frequency bands higher than 125 Hz, the car-tire source show nonlinear

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characteristics as the drop height increases (impact force increases). However, as the maximum value of the impact force for the rubber ball source dropped from 100 cm or the car-tire source dropped from 20 cm is relatively close, it cannot necessarily be explained only by nonlinearity due to impact force. In other words, the difference between the bang machine and the 100 cm rubber ball is probably due to both the nonlinearity of the impact force and the excitation frequency char- acteristics.

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Reduction of transmitted impact sound

Reduction of transmitted impact sound

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(dB)

(dB)

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63 125 250 500 1000 2000 4000

63 125 250 500 1000 2000 4000

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Tire_Floating floor_40cm Tire_Floating floor_20cm Ball_Floating floor_50cm Ball_Floating floor_25cm

Tire_Floating floor_Bang Ball_Floating floor_100cm

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Octave band center frequency (Hz)

Octave band center frequency (Hz)

Figure 4: Reduction of transmitted impact sound pressure level by floating floor system.

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Reduction of transmitted impact sound (dB)

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Tire_63Hz Tire_125Hz

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Floor impact sound pressure level of concrete slab (dB)

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Reduction of transmitted impact sound (dB)

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Tire_4000Hz

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Figure 5: Relationship between floor impact sound pressure level of concrete slab and reduction of transmitted impact sound by the car-tire source.

Floor impact sound presuure level of concrete slab (dB)

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15

Reduction of transmitted impact sound (dB)

10

5

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10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85

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Ball_63Hz Ball_125Hz

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Floor impact sound pressure level of concrete slab (dB)

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Reduction of transmitted impact sound (dB)

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Ball_1000Hz Ball_2000hz

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Ball_4000Hz

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Figure 6: Relationship between floor impact sound pressure level of concrete slab and reduction of transmitted impact sound by the rubber ball source.

Floor impact sound pressure level of concrete slab (dB)

Figure 5, Figure 6 show the relationship between the bare floor impact sound pressure level and the reduction of transmitted heavy-weight floor impact sound level by frequency band for the dry- type floating floor. It can be seen that there is no constant relationship between the floor impact sound pressure level of concrete slab and the amount of reduction, and the tendency differs considerably depending on the car-tire source and the rubber ball source.

In order to remove the effect of excitation frequency characteristics from the reduction of trans- mitted floor impact sound level, the floor impact sound level of concrete slab normalized in the 63 Hz band was subtracted, as shown in Equation 1 below.

∆𝐿𝐿𝐻𝐻−൫𝐿𝐿 𝑖𝑖 , 𝐹𝐹 𝑚𝑚𝑚𝑚𝑚𝑚,𝑠𝑠 −𝐿𝐿 𝑖𝑖 , 𝐹𝐹 𝑚𝑚𝑚𝑚𝑚𝑚,𝑠𝑠,63 ൯ (1)

where the ∆𝐿𝐿𝐿𝐿 is the amount of the reduction of transmitted floor impact sound level, 𝐿𝐿 𝑖𝑖 , 𝐹𝐹 𝑚𝑚𝑚𝑚𝑚𝑚,𝑠𝑠 is the floor impact sound level of concrete slab, and 𝐿𝐿 𝑖𝑖 , 𝐹𝐹 𝑚𝑚𝑚𝑚𝑚𝑚,𝑠𝑠,63 is the floor impact sound level of concrete slab in 63 Hz band.

Figure 7 shows the results of Equation 1. The figure shows that up to the 500 Hz band, the differ- ence between the impact source and the drop height (impact force) is relatively small, and the fre- quency characteristics are relatively similar.

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70

70

Tire_Floating floor_40cm Tire_Floating floor_20cm

Ball_Floating floor_50cm Ball_Floating floor_25cm

Tire_Floating floor_Bang

Reduction of transmitted impact sound by correction (dB)

Reduction of transmitted impact sound by correction (dB)

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Ball_Floating floor_100cm

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63 125 250 500 1000 2000 4000

Octave band center frequency (Hz)

Octave band center frequency (Hz)

Figure 7: Reduction of transmitted impact sound by floating floor system corrected by floor impact sound of concrete slab. Therefore, using the above results as a case study, the reduction of transmitted floor impact sound level of the rubber ball (100cm) was estimated from the value of the bang machine with Equation 2.

∆𝐿𝐿𝐿𝐿, 𝐻𝐻(2) = ∆𝐿𝐿𝐿𝐿, 𝐻𝐻(1) −൛𝐿𝐿 𝑖𝑖 , 𝐹𝐹 𝑚𝑚𝑚𝑚𝑚𝑚,𝑠𝑠,𝐻𝐻(1) −𝐿𝐿 𝑖𝑖 , 𝐹𝐹 𝑚𝑚𝑚𝑚𝑚𝑚,𝑠𝑠,63,𝐻𝐻(1) ൟ

+ ൛𝐿𝐿 𝑖𝑖 , 𝐹𝐹 𝑚𝑚𝑚𝑚𝑚𝑚,𝑠𝑠,𝐻𝐻(2) −𝐿𝐿 𝑖𝑖 , 𝐹𝐹 𝑚𝑚𝑚𝑚𝑚𝑚,𝑠𝑠,63,𝐻𝐻(2) ൟ (2)

where the 𝐻𝐻(1) is the bang machine, and 𝐻𝐻(2) is the rubber ball. The estimated and measured results are shown in Figure 8. The figure shows that the results cor- respond relatively well. In this study, the difference was approximately 4 dB in the 500 Hz band and below.

20

Reduction of transmitted impact sound

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(dB)

0

63 125 250 500 1000 2000 4000

Ball 100cm_Estimated value Ball 100cm_Measured value

-10

Octave band center frequency (Hz)

Figure 8: Estimated and measured values of reduction of transmitted impact sound by floating floor system for the rubber ball source.

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4. CONCLUSIONS

This manuscript discusses the reduction of transmitted floor impact sound level due to the change in impact force by varying the drop height of the car-tire and the rubber ball. The results suggest that the difference in the reduction of transmitted floor impact sound level between the car-tire and the rubber ball cannot be explained only by nonlinearity due to the impact force for the dry-type floating floor.

It was also suggested that the reduction of transmitted floor impact sound level of the rubber ball could be estimated from the reduction of transmitted floor impact sound level of the car-tire by con- sidering vibration frequency characteristics. 5. REFERENCES

1. JIS A 1418-2:2019, Method of measuring the floor impact sound insulation performance of build- ings - Part 2: Method by standard weight impact source (2019). (in Japanese) 2. JIS A 1440-2:2007, Method of measuring the floor impact sound level reduction of floor surface construction on concrete floors in a laboratory - Part 2: Method using a standard weight impact source (2007). (in Japanese) 3. Shunsuke, N., Junichi Y., Study on reduction of floor impact sound with wooden floating floor and application to actual buildings, Journal of Environmental Engineering (Transactions of AIJ), Vol.80, No.714, pp. 629-638 (2015). (in Japanese) 4. Ryuta, T., Experimental study of the reduction of transmitted impact sound level of floating floor system and tatami due to differences in impact force characteristics, 2022 Spring Meeting Acous- tics Society of Japan, March (2022). (in Japanese) 5. JIS A 1440-2:2007, Acoustics - Laboratory measurements of the reduction of transmitted impact sound by floor coverings on a solid standard floor - Part 2: Method using standard heavy impact sources (2007). (in Japanese)

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