It would depend on what you mean by volume (doesn't it technically depend on the listener's amplification?) and which scale (linear ratio of maximum, RMS, decibels, for examples) you wish to use to describe it.
You've already stated that the highest value (peak) of a short section can give an indication of how "loud" it is. You might want to compare its distance to the average value to offset any off-centre waves.
There is easy-to-find information on the internet about calculating RMS and DB reduction.
