Members rasputin1963 Posted May 17, 2007 Members Share Posted May 17, 2007 OK, here goes-- the ultimate embarrassing noobie question regarding audio, but hopefully one of you will answer it for me, once-and-fer-all: How comes it that the metering of audio has the 0.00dB value as being the loudest permissible sound in a recording? It seems to me (in my naive, intuitive way), that a meter reading of 0.00dB would be the quietest audio one could record. Then some arbitrary base-10 number as the loudest, like, I dunno, 100 or sump'n.... Don't get me wrong-- I mean, I use this value correctly now, i just don't understand WHY it has to be this way. Hey, I toldja it was an embarrassing question. i hope you won't just answer with, "Because, it just IS." Link to comment Share on other sites More sharing options...
Members steveg Posted May 17, 2007 Members Share Posted May 17, 2007 Because we said so!! Actually, not stupid question at all, I really don't know exactly why. My guess would be that is represents a baseline, a threshold which is simply a starting point for relative measure. It allows you to set different equipment to have 0 represent different reference voltages, i.e. +4 versus -10. It allows one to print a sine wave to a recorder and then align that playback on another machine and have them "agree" on the overall level. Link to comment Share on other sites More sharing options...
Members ggm1960 Posted May 17, 2007 Members Share Posted May 17, 2007 The simplist answer is that dB's are a reference measurement expressing the difference between in and out. 0dB is unity gain. I learned all about it in tech school so long ago I really remember very little. In my line of work (avionics communications gear) we often look at frequency rolloff where the usable frequency range falls between the rolloff points like -3dB down or -6dB down to either side of the center frequency.I know there are other techs out here that could probably explain it better.http://www.tpub.com/neets/book11/45e.htmhttp://www.sfu.ca/sonic-studio/handbook/Decibel.htmlhttp://www.phys.unsw.edu.au/jw/dB.html Link to comment Share on other sites More sharing options...
Members philbo Posted May 17, 2007 Members Share Posted May 17, 2007 Yup, you got it Greg! In the odd world of logarithmic math, 0 means 100%, (log of 1 = 0 ) and anything over 100% is clipped & distorted. There is a place for dB's above zero - - amplifiers. Because what comes out is greater than what went in. Good to see my buddy & band mate Greg hanging out here with me at HC! Link to comment Share on other sites More sharing options...
Members Billster Posted May 17, 2007 Members Share Posted May 17, 2007 Yup, you got it Greg! In the odd world of logarithmic math, 0 means 100%, (log of 1 = 0 ) and anything over 100% is clipped & distorted. I'll add that what the negative dB readings represent is the audio headroom. If your signal is at -6 dB, you have 6 dB of level you can add before you go into overload and distortion. "0 dB" means you can't go any higher without overload - you have zero headroom left. Link to comment Share on other sites More sharing options...
Moderators Lee Knight Posted May 17, 2007 Moderators Share Posted May 17, 2007 Let my buddy Nigel explain... Nigel: Eleven...eleven...eleven... Marty: ...and most of these amps go to ten... Nigel: Exactly Marty: Does that mean it's... louder? Is it any louder? Nigel: Well, it's one louder, isn't it? It's not ten. You see, most... most blokes, you know, will be playing at ten. You're on ten here... all the way up... all the way up. Marty: Yeah... Nigel: ...all the way up. You're on ten on your guitar. Where can you go from there? Marty: I don't know... Nigel: Nowhere. Exactly. What we do is if we need that extra... push over the cliff... you know what we do? Mart: Put it up to eleven. Nigel: Eleven. Exactly. One louder. Marty: Why don't you just make ten louder and make ten be the top number... and make that a little louder? Nigel: These go to eleven. Link to comment Share on other sites More sharing options...
CMS Author MikeRivers Posted May 17, 2007 CMS Author Share Posted May 17, 2007 How comes it that the metering of audio has the 0.00dB value as being the loudest permissible sound in a recording?I assume that you're talking about a digital recording. "dB" by itself is kind of meaningless. It's a ratio so it has to be relative to something. In the digital world, we talk about dB relative to the full scale value (all the bits turned on). The number can't get any larger than this, so it's the highest level you can achieve. The accepted correct nomenclature is 0 dBFS (for "full scale"). In the analog world, often 0 dB represents the VU meter reading for the nominal system level which allows for some headroom. So the meter might go to +20 in a system like that. You'll find that a lot of mixers today have 0 in the middle of the meter scale. The classic VU meter has full scale at +3. Link to comment Share on other sites More sharing options...
Members flatfinger Posted May 17, 2007 Members Share Posted May 17, 2007 Let my buddy Nigel explain... Nigel: Eleven...eleven...eleven... Marty: ...and most of these amps go to ten... Nigel: Exactly Marty: Does that mean it's... louder? Is it any louder? Nigel: Well, it's one louder, isn't it? It's not ten. You see, most... most blokes, you know, will be playing at ten. You're on ten here... all the way up... all the way up. Marty: Yeah... Nigel: ...all the way up. You're on ten on your guitar. Where can you go from there? Marty: I don't know... Nigel: Nowhere. Exactly. What we do is if we need that extra... push over the cliff... you know what we do? Mart: Put it up to eleven. Nigel: Eleven. Exactly. One louder. Marty: Why don't you just make ten louder and make ten be the top number... and make that a little louder? Nigel: These go to eleven. nigel has evidentally been training allot of M.E.'s on the use of limiters lately!!!!!!!!!!!!!!!!!! Link to comment Share on other sites More sharing options...
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