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.
Hu ḓo vha na u fhambana-fhambana ha volumu dza vhavhali. I iledzeni arali volumu ya hone i nṱhesa lune ya khathuwa, kana (zwiṅwe zwo ḓoweleaho) arali i fhasi lune ni si kone u pfa zwine zwa khou ambiwa ni songo sedza mafhungo o ṅwalwaho.