Hey Bobbsy,
Thanks for taking the time to explain all this to me.
Yes I saw a DIY version of the Reflexion filter on youtube - I figured there must be commercial versions out there. My house does back onto a train line; trains go by every 20 minutes or so, but I presume if a train goes past while I'm recording a specific line I can just re-record it and then edit the damaged one out? Apart from that it's pretty quiet. What about the computer humming, that kind of thing? Does the filter take care of those little noises?
I've yet to see a home made imitation of the Reflexion filter that did the same job--but maybe I'll be surprised some day! Yes the Reflexion filter will help with sounds coming from behind it but not so much if the sound source is behind the speaker, i.e in the direction the mic is pointing. However, you are entirely right that you can just take a swig of coffee and continue after the train, editing later. Frankly, I've know few people who can speak continuously for 20 minutes without a sip of water or something anyway (excluding my wife--she could talk for Wales).
As for other noises, I'm going to have to get slightly technical here. There are two things that will affect how much you pickup of room noises like computer fans and disks: distance and the mic pattern/pointing:
1. Distance. Sound follows what is know as the "inverse square law". This means that each time you double the distance from a sound source to a microphone, you quarter the amount of sound arriving at the mic. If you normally speak 1 foot from the mic and move to 2 feet, the amount of sound getting to the mic is a quarter what it used to be. You can obviously use this to help your noise issues...if you're 1 foot from the mic and the computer tower is 2 feet, the pickup from the computer noise is a quarter what it would be close up. If you can get the mic 4 feet from the computer, this changes to an eighth and so on. This means that the farther you can get from the computer, the less of an issue the noise will be. A filter around the mic and heavy curtains or something behind you will help even more--I often recommend building a simple frame out of PVC pipe and hanging duvets or movers blankets on it to position behind the speaker--then be packed away under a bed when you're done.
2. Mic pattern and placement: All the mics you should consider (and by far the most common mics anyway) have what is known as a "cardioid pattern". This means that the pickup directly behind the mic is greatly reduced over the pickup in front of it. You can use this trait by planning how you lay things out--if you can get your humming computer directly behind the mic, this (in conjunction with distance and soft stuff behind you to kill reflections) will pretty much eliminate computer noise.
If worst comes to worst, invest in a KVM cable and remote the computer tower well away from the keyboard and monitor where you sit.
I don't need MIDI capability at all. All I'll be doing is straight voice recording. Remembering that I'm a complete novice (with a good analytical mind), which DAW is the most user-friendly?
Beware anyone who states with great assurance that DAW xxxx is the easiest to use. It really comes down to personal preferences and how you get on with the user interface. A boring anecdote would be that, at work, I used to use a DAW called Protools all day, every day. Despite formal training and all the practice, even years on I never felt completely at home with PT. However, when I tried Audition, it was like "coming home" and everything fell into place rapidly. However, there are others who feel exactly the opposite--it's down to the individual.
Since most DAWS offer a free trial, I suggest you download a couple and just play while you're thinking about it. Both Reaper and Audition mentioned above will let you try for free and many others will as well and, until you have a mic and interface you can just play with some pre recorded music or voice files--an audio book for example. However, with either them do expect a steep learning curve if you've never recorded and mixed before.
Also, given my situation, what is you recommendation for brand audio interface and mic?
If 20 people reply to the question you'll get 40 answers! Personally, I'd suggest an sE Electronics 2200A Cardioid (there's a more expensive one with switchable patterns that you don't need) for the mic and maybe a Tascam US 122 for the interface. Or you could look at the M Audio M Track--it's new and I haven't tried it but I've had good results with the previous version. However, prepare to be confused as others reply!
Is there anything else I'll need other than those 4 elements (mic, filter, DAW and audio interface)?
Yes, monitoring. You need to be able to hear what you're recording and mixing. Ideally you'd have good headphones to use while recording and decent monitor speakers for the editing and mixing. In your case, you might be able to get away with doing everything on headphones but you'll need to take time to "learn' your sound. Do a few minutes, burn it to CD then play the results back on lots of different systems to see how it sounds in the real world. You'll gradually learn how things need to sound on the headphones to sound good everywhere else. With monitor speakers, you still need to learn them but the process tends to be easier and faster.
Now that I've totally confused you, I'm making a pot of tea!