Bignerd, I don't really have any experience in pro-sound applications; I just have played around some (maybe too much) with prosound drivers.
I have no specific knowledge of the effect of a crowd on room acoustics. I'd guess a crowd of people would be more absorptive than diffusive, such that the power requirement to meet a given SPL in a full auditorium would be several dB more than if the room was empty. And since most absorbers are more effective at short wavelengths (high frequencies) than at long wavelengths (low frequencies), the spectral balance of the soundfield would be tilted downward somewhat by adding a crowd of people. But I have no idea of the specifics of such effects.
Duke
I have no specific knowledge of the effect of a crowd on room acoustics. I'd guess a crowd of people would be more absorptive than diffusive, such that the power requirement to meet a given SPL in a full auditorium would be several dB more than if the room was empty. And since most absorbers are more effective at short wavelengths (high frequencies) than at long wavelengths (low frequencies), the spectral balance of the soundfield would be tilted downward somewhat by adding a crowd of people. But I have no idea of the specifics of such effects.
Duke