Since now there are 76 identical trombones,
therefore the whole group will be 76 times stronger than if there is only one trombone
given that all other things being equal (such as distance and orientation). A
dB figure is simply a ratio, in the case of the one trombone, with some
reference sound intensity level, such as 10^-12W/m^2.
To multiply two numbers, add the log of the two numbers.
One trombone is 70 dB, and this is multiplied by
a ratio of 76 = 10 * log (76) = 18.8 dB.
Therefore the resulting sound intensity of the 76 identical
trombones is:
70 dB + 18.8 dB = 88.8 dB
Answer:
88.8 dB
