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Im just wondering, as there are lots of kinds noise that creep into our recordings. what are the typical frequencies where noise is mostly present as so I can apply filters etc.. And also, what type of filter would one suggest applying when recording to minimize and attain the best SNR?
(noise such as wind/electrical etc..)
60 Hz is a common electrical hum in the US. A HPF can sometimes cut down on LF wind rumbles: play around with the roll off frequency.
The major issue with trying to filter out undesirable noise is that it is very often broad-spectrum (wind, etc). If you try using filters to get rid of the noise, you end up losing a lot of desirable information as well, and color the sound.
The best approach is to avoid undesirable noise as much as possible: use the highest-quality preamps you can afford, use proper wind protection, make sure your cables have good shielding and your power is as clean as you can make it.
Speaking as a post-sound person, I'd rather have a noisy recording than one with filters applied in the field. As Joe said, do all you can to avoid wind noise, noisy mics, and other hums/buzzes you may pick up, but if it ends up in the recording, note it and see what can be done in an editing program.
I agree with Joe and VCProd, but would like to add two points that I believe require some emphasis:
1) Certain mics are often used in specific situations not only because of practical reasons, but also because of the unique signature they impart on the sound. Application of wholesale filters in the recording process will not be appreciated and could get you fired, or worse...
2) It can often be a pain in the butt to spend hours removing unwanted noise that could easily have been avoided or at least minimised with careful planning. However, that is waaaaaaaaaaay more preferable than having to try and put back wanted noise that has been removed erroneously in the recording process.
broadband noise such as wind, air traffic, and the generic city background occupies more than one frequency, and can be found in whole parts of the spectrum. you can get successful results by multiband dynamics processing, or a broadband noise reduction system.
lights whine at high frequencies, power hum is at 50 or 60hz depending on your location. city rumble can go down to infrasound. w/ airplanes passing overhead v.high in the sky i've so far had a descending low frequency going from 200+hz down, but no idea how to automate cleaning that. for everything that stays at a single frequency you can do a spectrogram and attenuate with a surgical EQ..
