Any two or more frequencies can and will interact with each other and possibly create a new frequency, the "beat frequency" as Jay pointed out above. This may happen across the entire spectrum, but it is only relevant to us, if the resulting "beat frequency" falls in the audible range. If and when it does 48kHz can easily sample th result of this effect. Once the signal has been digitized there will be no more interaction of frequencies. Only once this is played back could there be new beat frequencies, created by the room - if any.
So for this phenomenon, as Jay says, we don't need more than 48kHz.
Actually, since we don't want random interaction of frequencies and beat frequencies, this is an argument for lower sample rates