45.4 Application in Structures

Back

In this section, we present an example of

modeling with significant analytical accuracy,

and discuss the application of the SEA method

for structures.

45.4.1 Application for Prediction

of Noise in a Tractor Cabin

Figure 45.3 shows a model of the tractor cabin.

This figure shows that the cabin consists of a

floor, a door, a ceiling, and other components.

Figure 45.4 presents the power flow relationships

within the cabin [9,10].

FIGURE 45.6 The configuration of the building.

42

1

2 3

4

5

6

7

8

9

10

11

12

13

14 15

16

17 18

19

20

39

40

30

29

25

26

32

31

28

24

38

23 37

22

27

21

36

34

35 41

33

FIGURE 45.7 The power flow relationships between structural subsystems in the entire building.

70

65

55

50

45

40

125 160 200 250 315 400 500 630 800 1000 1250

Frequency [Hz]

Experimental Value

Analytical Value

Sound Pressure Level [dB]

FIGURE 45.5 Results of estimating the sound pressure

level in a cabin.

Statistical Energy Analysis 45-7

© 2005 by Taylor & Francis Group, LLC

The results obtained for the cabin are shown in Figure 45.5. According to this figure, the disagreement

between the computation and the measurement was found about 2 dB in the medium- to high-frequency

band.

45.4.2 Application for Prediction of Noise and Vibration in a Building

Consider a two-story laboratory reinforced with

concrete [11]. The building configuration is shown

in Figure 45.6. This building comprises a driving

room, an acoustical laboratory room, a computer

room, a measurement room, an equipment room,

and others.

We modeled the structural subsystem using

I-, L-, or T-type connected points, and the

acoustic subsystem as an element shown in

Figure 45.6.

The SEA model constructed in this manner is

composed of 61 elements, and has 244 connecting

points. Subsystems 1 to 17 and subsystems 19 to 42

are concrete components. Subsystem 18 and

subsystems 43 to 48 are plasterboard components;

subsystems 49 to 55 are room components; and subsystems 56 to 61 are cavity components. For example,

Figure 45.7 shows the power flow relationships between structural subsystems in the entire building,

while Figure 45.8 shows them in the acoustical laboratory room. Here, the thin-dotted, dotted, and solid

lines indicate the I-, L-, and T-type combinations, respectively. Subsystem 53 is the room component,

and it is connected with all structural components shown in Figure 45.8. The plasterboards located

between the computer room and the measurement room are considered as a partition; therefore,

connections between subsystem 49 and subsystems 56 to 59 (cavity components), and subsystem 50 and

subsystems 60 and 61 (cavity components) are derived from nonresonant modes.

The results obtained for some other rooms are shown in Figure 45.9. Computing accuracy in

this building is worse than in the cabin because the structure of this building is complicated, although

the differences between the computed values and the measured values were approximately 4 dB in the

medium- to high-frequency band.

The computations take approximately 10 sec, so the workload on the personal computer is quite light.

53

42

4

5

37

23

24

28

14

15

31 6 7 8

10

9

38

FIGURE 45.8 The power flow relationships in the acoustical laboratory room.

Frequency [Hz]

Sound Pressure Level [dB]

Re : 2×10−5 [Pa] 20

30

50

60

70

31.5 63 125 250 500 1000

40

Experimental Value

Analytical Value

FIGURE 45.9 Estimated sound pressure level results

for other rooms.

45-8 Vibration and Shock Handbook

© 2005 by Taylor & Francis Group, LLC

Навигация