Levels 85 db optimum based on equal loudness curves and typical listening levels 
Listening room acoustics Sound will appear to be louder in a room with more reflective surfaces as well as being harder to locate directionally. The room may need to be treated with absorptive materials to dampen its resonant characteristics. 

The effect of listening room acoustics can be minimized by using near-field loudspeakers for monitoring. 

Speaker placement near field speakers minimize room acoustics otherwise care needs to be taken in room design 
Headphones eliminate influence of room acoustics but alter stereo perspective and increase fatigue 
Cue mixes and performer monitoring necessary when recording ensembles with isolation and necessary when overdubbing