An operator in a textile mill is operating six machines. If the sound pressure levels of each machine at his position are given in Table Q2(b):

(i) Determine the total sound pressure level (in decibels) and total mean square pressure (in N/m2 ) produced by all six machines at the operator position.

(ii) If the two machines, M1 and M2 are turned off, and assuming that total sound pressure level is 120 dB, analyze the sound pressure level of the background noise (in decibels) and its mean square pressure (in N/m2 ) at the operator position.

(iii)If the data from Table Q2(b) is converted to octave band as shown in Table Q2(c), examine the total sound pressure level in dB(A) and total mean square pressure (in N/m2 )

(iv) Describe briefly three method to control the noise if the answer in Q2(b)(iii) is SPL > 85 dB(A).

9P Table Q2(b) Machine No. Level (dB) M1 M2 8Q M3 9R M4 M5 6T M6 8U 75 P=1Q=2 R:3 5:4 T=5 U=6 Machine No. 250 500 1000 2000 4000 8000 Table Q20) Level (dB) 9P 8Q 9R 75 6T 8U A weighting (dB) -8.6 -3.2 0 1.2 1