Audio background noise

[Delta2]

I don't know if I'm breaking any rule, I'm just interested in pure technical information, if so please forgive me

The better way I can explain this type of audio noise is this way :

Imagine I take my video camera and film a movie in my TV

The resulting audio will sound distant, if it were in a tunnel, or something like that. Or imagine a audio from a piracy CAM release, it is the same noise : distant, some background noise

What I want to know is the technical name for that type of noise, what is the technical name of that effect in audio ? and how can I reduce it

[StickHorsie]

Actually, it's called "noise" :D (I kid thee not.)

But, more specifically, there's:
.
- totally non-continuous random noise, like clicks, pops & scratches (on records) people talking, phones ringing, applause, laughter, etc etc. Clicks can be reduced with any declicker program (I use WaveLab's declicker for that), pops & scratches usually need tediously manual labor. "Public background noise" (as long as its volume is lower than the audio you wish to keep) can sometimes be made a little less irritating by using an expander or noise gate, which can be found in any decent audio editing program. Expanders and noise gates cause the overall volume to drop in the quieter parts where the "public noise" is the most irritating - unfortunately this also causes the main audio to drop in volume in the same parts, so at best you'll get a result that's "a little less bad". "Single end" noise reduction programs / plugins operate on the same principle, even though they're a bit more specialized / advanced.

- one or a few peaking / resonating frequencies, usually caused by "make do" microphone placement (like, when making a cam copy, or the "tunnel noise" you mentioned). Can be identified with a frequency analyzer (I use the one in SoundForge) and simply be equalized away for 50-100%. Sometimes, the lower and higher frequencies (below 40 / 50 Hz and above 10 / 12 kHz) contain nothing you wish to keep and can also be filtered out.

- continuous uniform noise, like hum, hiss, motor or fan noise. These can (sometimes spectacularily well) be removed with any "active noise removal" program (I use CoolEditPro for that, but DartPro can also yield nice results) which uses a "noise print" (= a part of the audio that only contains the background noise). Unfortunately, it's not the easiest thing in the world to find optimal settings if you don't want any audible artefacts.

For any further info on specific audio tracks, you'll need to attach a few minutes of the actual audio, including a very quiet part in case I need to make a noise print.