[GraemeJ]

Can you elaborate?

Normalising is a simple mathematical process that increases the overall level, such that the peak level is at whatever you have set it at (usually 0dB, or marginally less). If the original peak level was lower that this, then the track will, indeed, sound louder.

However, due to the way our ears work, the perceived volume of a track is actually related to the RMS average of the whole track and normalising does not change that average - it remains the same.

To take a practical example, a track with a wide dynamic range (say an orchestral piece with a solo instrument) with its peak level set to maximum will still sound quieter than a (say) heavy metal track, where it is almost brick-walled in terms of level and therefore has a much higher average level.

If you really want to make all your tracks have the same perceived volume, then it is necessary to compare all of them with each other and adjust the average level to the be the same for each one.