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.
Ye normal que i haiga variacions de volumen entre lectors. Refusa-las nomás quan lo volumen sía tant alto que lo rechistro satura, u (mas comunment) si ye tant baixo que no puetz sentir lo que s'ha dito sin la referencia d'o texto escrito.