Building Services Engineering 5th Edition Handbook

340 Room acoustics
100
90
80
70
Sound pressure level (dB)
60
50
40
30
20
10
0
31.5 63
125 250 500 1000 2000 4000 8000
Frequency (Hz)
NR 35 NR 40
NR 50 NR 55
Fan SPL dB
NR 45
14.4 Noise ratings, solution to Example 14.8.
It should now be possible to check manually any sound pressure level against noise rating.
Once the frequency that produces the greatest sound pressure level from the sound source is
identified, other SPL values can be obtained for the peak frequency to check which NR is not
exceeded.
The room does not exceed the NR 55 curve data but it does exceed NR 50. Plot the chart with
the spreadsheet functions for NR 35 to NR 55 and with the room noise SPL. The spreadsheet will
produce curves for six sets of data, so five NR curves and the one room curve can be displayed
on one chart. The results are shown in Fig. 14.4.
Questions
Questions 1 to 31 do not need to be evaluated on the worksheet. The worksheet is to be
used for Questions 32 onwards. The solution to Question 32 is shown on the original file
DBPLANT.WKS. Solutions to descriptive questions are to be found within the chapter, except
where specific answers are provided.
1. List the sources of noise that could be found within an air-conditioned building.
2. What is meant by noise?