Please do not feel like an idiot as this is a good question. It could mean what is going on downstairs at the nightclub but that's not it.

What noise floor refers to is generally a specification utilized with many different kinds of condenser microphones, preamplifiers, amplifiers, analog tape noise. In short, at the bottom of your dynamic range at the lowest point of usable dynamic range is where the noise or noise floor is.

Conversely and oppositely your "headroom" is in the loudest point or peak of your dynamic range before distortion and/or clipping occur, both in amplifiers of all types and you're recording medium. Professional equipment generally has more headroom than "prosumer" and consumer equipment has. In old-fashioned (now I'm showing my age) analog recording 0 VU recording level usually has a headroom of about 12 to 15 DB higher than 0. But in digital recording 0 "VU" is as far as you can go without horrible distortion, so in digital recording you must make sure that your levels average between -18 to -15 DB below 0 and stay below 0. "VU" stands for volume units which refers to a meters ballistic characteristics, i.e. how fast it rises and falls. "PPM" stands for peak program meter and as its name implies, its ballistics show your peaks faster than a VU meter indicates and thusly is better for digital recording purposes.

S/NR or "signal to noise ratio" is another way to express " noise floor" and is generally expressed in DB with reference to the average or highest level you can record at.

I hope this makes some sense to you and helps you and your understanding towards making better recordings?

If you splash water on me I generally yell " I'M DISTORTING, I'M DISTORTING"
Ms. Remy Ann David
Wicked audio witch of the East

The Yamaha "Sound Reinforcement Handbook" is a treasure trove of info about just these types of questions. From "noise floor" to wiring diagrams for all connectors and how to solder them, to explanation of dbv,dbfs, dbu...etc. I highly recomend it.

an easy very simple and VERY BASIC but somehow parctical tip is:

switch on all your gear, open all channels on your mixer or soundcard plug in some mics and basically connect al lot or all your equipment like you would record... now be utterly silent and push all the faders up to max including the master, you will hear a big schhhhhhhhhhhh..... and maybee some low rumble as well that is initially your overall noise floor... ok keep in mind that the mics will "record or pick up" some excisting ambient noise, as there is no total silence... but the lower this noise is you will hear the lower your allover noise floor is... all the noise your gear produces without feeding any sound...

sometimes this method can help finding the noisiest "element" in your chain... just plug / switch one by one after the other to max volume... and then in different orders and so on... it's not accurate at all but it can help without an analyser to find the "bad" apple, a very noisy mic pre for example...

hope it helps

A very good point axel! Turn on. Tune in. And listen carefully to absolutely nothing! That will certainly let you know what's really going on, inside your stuff. (Unterminated microphone inputs should be loaded with a microphone, otherwise they get really funky sounding. A passive dynamic microphone, will let you hear your preamplifier's noise better as compared to an active condenser microphone which will produce its own noise)

CAN YOU KEEP IT DOWN, I'M ON THE PHONE!
Ms. Remy Ann David

A very good point axel! Turn on. Tune in. And listen carefully to absolutely nothing! That will certainly let you know what's really going on, inside your stuff. (Unterminated microphone inputs should be loaded with a microphone, otherwise they get really funky sounding. A passive dynamic microphone, will let you hear your preamplifier's noise better as compared to an active condenser microphone which will produce its own noise)

CAN YOU KEEP IT DOWN, I'M ON THE PHONE!
Ms. Remy Ann David

i still like some potatoes.

thanks so much everybody...
i have just ordered that book, hopefully it will answer all my dumb questions so you guys wont have to.....
thanks again guys