When multiple sound sources are combined, the total sound level can be found using the formula:
Ltotal = 10 log10 (N) + Lsource
where N is the number of sound sources and Lsource is the sound level of each individual source.
In this case, we have 39 singers and each singer produces a sound level of 70.6 dB. Substituting these values into the formula, we get:
Ltotal = 10 log10 (39) + 70.6 dB
Ltotal = 10 (1.591) + 70.6 dB
Ltotal = 88.5 dB (rounded to one decimal place)
Therefore, the sound level produced by a chorus of 39 singers singing at the same intensity at approximately the same distance as the original singer would be approximately 88.5 dB.