Initial data for calculation options

Task for self-training

To determine the effectiveness of application to eliminate the outer screen in the production room if the levels of sound pressure generated by the source of noise at frequencies f₁ and f₁ are respectively L₁ and L₂, permissible sound pressure levels at these frequencies respectively L_1psl and L_2psl (table 4.1).  Screen with size (h)×l is stood at a distance and from the source of noise, and distance from the screen to the workplace (b). Data for calculation options are given in table 4.2.

Table 4.2

Initial data for calculation options

 

№ option

h×l

а

b

f₁

f₂

L₁

L₂

Type of space

1,3,13,19

1×1.5

Control

2,4,14, 20

1×2

0,5

2,5

Working room

5,7,15,21

1×2.5

0,7

Engineering Bureau

6,8,16,22

1×3

2,2

Laboratory for experimental works

9,11,17,23

1×1.5

0,8

2,1

Premises with noisy aggregates computing

10,12,18,

1×2

0,7

Computer Programmers

4.2. Design of sound-absorbing siding of the production premises

 

Facing internal surfaces of industrial premises with sound-absorbing materials provides a significant reduction in noise. The greatest acoustic effect of sound absorption is observed in the zone of the reflected sound, in points of the premises where the direct sound, the effectiveness of acoustic absorption is significantly reduced.

The use of sound-absorbing facings is advisable when at the calculated points in the area of reflected sound it is required to reduce the sound level by no more than 10 ... 12 dB, and at the calculated points at workplaces – by 4 ... 5 dB.

Sound-absorbing facings are placed on the ceiling and on the upper parts of the walls. Maximum sound absorption is achieved when facing at least 60% of the total area of the enclosing surfaces of the room (excluding the area of the windows). To calculate the sound absorption, you need to know the acoustic characteristics of the room: B – room constant, m²; A – equivalent sound absorption area, m²; α is the average sound absorption coefficient.