Following on from Chris' original query, I have a related one.
I have a number of radio shows as MP3 files which I want to listen to in the car. A typical show (mostly Radio 4 comedies) has a lot of talking and occasional bursts of noise (laughter).
In order to hear these in the car over road noise I have to have the volume turned up very high, which of-course then results in a deafening roar if the audience laughs. The same is true of live broadcasts, of-course, but having them as MP3 files gives me an opportunity to do something about this. (I have the same problem with audio books which I like to listen to in the car on long journeys.)
Any tips for how to improve this situation? Is it as simple as using some kind of automatic gain? I'm a complete novice with all things audio!