Dave Liquorice wrote:

How long is a piece of string?

Yes, I appreciate the point.

Depends how wide a dynamic range
you're having to deal with and what the loud bits are.

Mostly, Audacity shows the range as from -20 dB to -6 dB but there are
occasional peaks of 0dB or above. All the files are of a man speaking,
whispering, and sometimes shouting.

If the "normal" speech has a dynamic range of 10 to 20 db a
compressor set at 2:1 to 3:1 with around 6 dB of gain reduction
happening ought to work reasonably well.

Sorry, I'm not sure what you mean by 6 dB of gain reduction. How does that
relate to Audacity's parameters of threshold, noise floor, and ratio?

Just looked at Audacity's compressor/limiter "effects" and they
aren't realtime.

I can see how that would be useful. I suspect that realtime would need
rather more processing power than I have available though. What software do
you favour?