Which is the more conventional / useful format when discussing such things? The Faber Acoustical iPhone meter gives the choice of A, C or Flat for Weighting, LP or LEQ for Level Type, and Fast, Slow or Impulse for Response. I've tended to use Flat, LP and Fast since getting the app.
The correct settings are A-weighted decibels, and slow response so that you can (visually) estimate an average value over a representative sample of your listening period. Better still is an Leq reading, which integrates everything during the measurement period (e.g., 60 sec) giving you a true average value. You can do this with the Faber app on the meter. Hold the phone vertically, otherwise the Leq option won't show.
As a guideline for repeated daily exposure to sound, try to keep your average 8-h exposure to 85 dBA. Don't worry about exposures below 75 dBA, as these add essentially nothing to your daily dose.
Noise dose is comprised of two equally important elements : the intensity and the duration. Since noise intensity doubles every 3 dB, the following are all equivalent exposures that one can use to manage daily exposures. Also, don't worry if a day goes over here and there, as it is the long-term average (from repeated daily exposures) that needs to be kept below 85 dBA.
85 dBA * 8h
88 dBA * 4 h
91 dBA * 2 h
94 dBA * 1 h
97 dBA * 30m
100 dBA * 15 m
103 dBA * 7,5 m
106 dBA * 3,8 m
109 dBA * 1,9
112 dBA * 1
115 dBA * 30 s
> 115 dBA : wear your hearing protectors !
These figures are for continuous noise, not impact (eg., hammer blows) or impulse (eg., gunshot) noise, which present greater risk to hearing. At all costs, avoid unprotected exposure to repeated impact or impulse noise. Save your hearing for music, your dopamine reward system will thank you.
Jan
Edit : Serge's post above (we posted at about the same time) mentions the flat and fast settings for measuring sound ; this is not ideal for determining average exposure to sound (music or noise). Use the A weighting (dBA) and slow. Also, it can be hard to determine an average value from a fast setting when the needle is bouncing around. The Lp setting on the the Faber app gives you the instantaneous sound level.