Question

A person standing a certain distance from eighteen identical loudspeakers is hearing a sound level intensity of 118 dB. What sound level intensity would this person hear if seven are turned off?

Answer 1

Total sound intensity level due to 8 speakers,

L (total) = 10 log (l_total / l)

L (total) = 10 log (18*l1 / lo)

L (total) = 10 log (18) + 10 log (I1 / Io)

L (total) = 12.55 dB + L1

sound intensity level due to one source, L1 = L(total) - 12.55 dB

L1 = 118 - 12.55

L1 = 105.44 dB

if seven are turned off, there are only 11 loudspeakers as source.

sound intensity level due to remaining 11  loudspeakers,

L = 10 log (7I1 / lo)

L = 10 log (7) + L1

L = 8.4509 + 105.44

L = 113.9 dB