C&V wrote:Reduce / remove background noise and enhance the sound of the voice
By far the best way is to minimise the background noise when you record - use a quiet room, avoid locations with a lot of echo, use the microphone reasonably close to the person that is speaking, record at a good level (high, but avoid distortion).
There is a "Noise Removal" tool in the Effects menu that can help to some extent, but if there is too much noise it will not be able to cope without damaging the audio that you want to keep.
Repairing a bad recording is very much a "last resort".
C&V wrote:Reduce whistle in voices (eg. one gentleman we record has a very pronounced way with his "s" in words - so it almost sounds like he is whistling when saying some words).
If you zoom in on a pronounced "sss" sound and select it, then use "Analyze > Plot Spectrum", you should be able to see a sharp peak somewhere around 3000 to 5000 Hz. See what frequency this occurs at, then use the "Equalizer" Effect to drop this frequency down.
There are effects called "De-essers" that do a similar thing, but in a more sophisticated way, but this simple method can help quite a lot. The Equalizer in Audacity 1.3.5 is a lot better than the one in Audacity 1.2.6
I am working on a De-esser plug-in at the moment (as and when I have time) and would be very interested in a sample of this whistling gentleman (for testing purposes). I could PM my e-mail address to you if you are able and willing to send me a short sample.
C&V wrote:then using the mic in function on audacity to get them onto my PC and start editing them
If you have a full size PC rather than a laptop, you should use "Line in" rather than "mic in" for better quality.
For Audacity 1.3 there is a lot of information about effects here:
http://audacityteam.org/manual/index.ph ... ffect_Menu