I this my sound dumb but when I was in the O.R one day and when I went to turn on the music the volume was -dB. I understand what it means but for other people they don't.

Why did they change the volume, most times its from 1,2,3,ect. Why did it get changed? Also on most low end audio (CD Player) it is still 1,2,3, ect, but it you spend 200$+ the volume is in dB. Just b/c I spend 200$+ on a CD plays does not mean I understand. Thanks for taking the time to read my dumb question, well more like a stupid rant.

The primary reason is that 1,2,3, etc. is an arbitrary scale. The dB scale -- if you've calibrated your system -- more closely represents what's happening to your output as you adjust your volume.

The concept is that if you calibrate your system, zero represents "reference" level which is often 75, 80 or 85 db, depending on the receiver. PLuses or minuses represent the deviation from your preset reference level in dbs which is the scale used to measure sound pressure (loudness).

However, I think you said you already understood this but what I really wanted to say is that the whole zero = reference level is kind of ruined by the fact that music and movies don't get recorded at exactly the same playback volumes so one CD at zero could be loud while another could be very soft, requiring adjustment.

Too bad they wouldn't standardize, at least for new. Or add a calibration code to the beginning of digital recordings that equalizes the SPL to match a standard reference level. Hey, you didn't read that. I'm off to the patent office. Well, once I invent it.....

Thanks for the explanation Murph. I've always just accepted that I vaguely understood this concept, but I've never really thought about it. My system is set so that if I set about -25dB or so I end up getting around 80dB on my RS meter (content dependent of course).

Is there a standard that recommends the way we calibrate our systems so that -25dB in my system would be the same as -25dB on your system with the same source material? I am now curious.

Use the internal test tones for your receiver. Most are -30db. This means they should read 75db on your SPL meter.

Dave,
Yup, working from home office today and just ran a quick check. When I go into test tones it automatically sets the volume at 0 and the reading is close to 75 dB in my room (a bit higher at 77 dB actually). I had not noticed that little detail before.

My amp lets me tweak the volume with the test tones so I could get it down to 75 or bump it up to 80. I assume this won't matter either way as the speaker leveling is all relative to each other. Please feel free to enlighten me if I have made a bad assumption.

Your good and have the right idea. Some amps calibrate to 75, others 80. The goal is to have all your speakers tweaked so they are equal at your main seating position. Usually each speaker takes from .5db or up to a few db, plus or minus, to even thm all out to say 75.

Also, don't be afraid to tweak a bit further to your liking. Once you get them set all perfectly equal, many people bump the center channel results up a db or two in order to get clearer dialog for TV and movies. If you find that you are always fiddling with the volume to hear speech better then lowering it again when loud sound effects occur, then this helps a lot and you can leave the remote on the coffee table where it belongs.

Other people like to bump their surrounds up a notch to highlight surround effects but too much and they get isolated to the speaker. Get it just right, and stuff blends and flies around the room, over walls, even your ceiling (see posts on "Master and Commander.")