There will be natural variations in volume between readers. Reject only if the volume is so high that the recording breaks up, or (more commonly) if it is so low that you can’t hear what is being said without reference to the written text.
Il sera natural variationes in volumine inter lectores. Rejecta solo si le volumine es assi alte que le registration se interrumpe, o (plus communmente) si illo es assi basse que tu non pote audir lo que es dicite sin referentia al texto scribite.