Not a great deal I can say on this subject except that you would be surprised at how many producers ignore this in the whole mass of audio that they are dealing with.
It is so easy to NOT hear noise when you are past the start of a track with all the components playing their bits. This is where headphones come into their own league.
Headphones can isolate noise because the sound is not washed out and saturated into the surrounding environment (speakers), but kept intact within the headphone’s sound field.
You hear amazing detail with headphones and it is this detail that exposes any anomalies in the mix.
Noise comes in many formats:
Clicks, hiss, low level rumble, pops, vocal sibilance etc should all be treated as noise. Some would debate sibilance or popping of ppp, bbb or ttt whilst singing as ‘singing’. I call it noise because it needs to be treated and removed.
It is good practice to leave a few seconds of lead-in to the song, where no instruments are playing and all you are hearing is the sound card and the gain settings of the mixer (hardware or virtual). Bear in mind effects and dynamics have inherent noise too and this can only be heard in isolation or during the lead-in. The lead-in will reveal any hums, hisses or rumbles. Because, once the music starts, they will be masked by the overlying sounds. It is also good practice to leave a few second of lead-out at the end of the mix to further check and analyze any anomalies that might have crept in unnoticed. It is at this point that you can check list the components that might cause any of these
Personally, I run a noise filter across my main stereo outs of my mixer (analogue), or master sub outs, prior to the sound card’s inputs, in order to remove any hiss or similar from the mix prior to the record master record stage.
For this, I use a Drawmer DF330. Some producers use noise gates across the mixer’s channels (if they have them) or across the main outs, much as I do.
In a virtual domain and working with a high bit depth like 24 bit, this particular problem is lessened to the point of negligence as the noise floor is almost non-existent.
Low level hum or rumble can be filtered out using a notch filter, band pass or a high pass filter. EQ can also help, but you can generally find the cause of low level hum to be an amp of some sort, monitor interference, low level earth loops etc.
Isolate and eradicate these prior to any recording or mixing. Try not to eradicate by using dynamics as this just add another generation of processing, but try to find the actual cause of the hum etc. and fix it.
Nowadays we have noise profile processing plugins that work by recording a noise profile of the audio you want to 'clean' and then using the printed profile to cancel (I use this term loosely) the noise from the audio.
As to which headphones I recommend? Well, that is down to budget and personal choice and whether you want isolation or mixing attributes, but the two I always recommend are the Sennheiser HD 650 and the AKG K701 (be aware that you would have to 'run' these in before they open up and mesmerize you).
They are both very good headphones and offer good detail, stereo imaging and noise isolation. However, they are great for mixing with as they are semi closed and offer some 'bleed'. If you want to truly isolate noise then any half decent isolation headphone will do as they offer no bleed and enclose the sound.