5 points for each Determine the NC ratings of the two enviro

(5 points for each) Determine the NC ratings of the two environments below. NC charts for each are on pages 3 and 4: 1. Freq 63125250 500 1000 2000 4000 8000 dB 57 55 49 44 43434 40 Freq63 125 250 5001000 2000 4000 8000 65 59 52 40 36 3 dB (2 points) By analyzing the test data of the two assemblies, describe the sound type and possible noise source for each environment. On your flash drive, refer to ASHRAE Applications Ch. 48, Figures 3 and 4 for guidance.

Solution

Given that in the problem thefrequency and sound levels for two environments,and we need to determine the NC ratings by using nc charts.

by analysing the NC curves the NC levels can be determined

for environment 1.. from the given data if we plot the source levels then it is nearer to 35-45.

and if NC 30 graph is selected for the given environment then the NC levels are as below.

for environment 2 if we plot the point source then it is nearer to NC 45-55 level graph will indicatesand for environment 2 NC 35 is selected,thenthe NC levels are as shown below

from the given standard values it can be conclude that the environment1 sound source is general office type

and the second environment sound source is factory light work.

the standard sound levels ranges for different environments as follows

environment

Range of NC levels

Factory – heavy work

55-75

Factory – light work

45-65

Kitchen

40-50

Sports area, swimming pool

35-50

Shop, department store

35-45

Restaurant, café.

35-45

General office

35-45

Private office, library

30-35

Home

25-35

Hospital ward

25-35

Concert hall

20-25

sound type: for environment the sound type to be quiet as it standardrange varies between 40-50and environment 1 sound level ranges between 35-45 hence it is the quite type sound

for environment the sound type to be noisy as it standardrange varies between 50-80 and environment 2 sound level ranges between 45-55 hence it is the noisy type sound

otave band center frequency	63	125	250	500	1000	2000	4000	8000
measured sound levels db	57	55	49	44	43	43	41	40
NC 30 levels from NC graphs	55	47	42	36	33	31	28	27
insulation required in db	2	8	7	8	10	12	3	13