The text does not prescribe one loudness level for every setting. Ask two questions:
Is the recitation being pronounced clearly?
Is someone nearby being disturbed?
If a praying person, patient, or sleeper is affected, reduce the volume. The three examples are explicitly named by the author. The larger application is to recite conscientiously without allowing one’s preferred sound level to disregard the people nearby.
Opening interactive controls...
Applying the volume condition
Etiquettes of Qurʾān Recitation — Sixteen Principles
The text does not prescribe one loudness level for every setting. Ask two questions:
Is the recitation being pronounced clearly?
Is someone nearby being disturbed?
If a praying person, patient, or sleeper is affected, reduce the volume. The three examples are explicitly named by the author. The larger application is to recite conscientiously without allowing one’s preferred sound level to disregard the people nearby.