Use SoX to amplify all WAV files in the current directory as much as possible without clipping

amplify_all.rb

#!/usr/bin/env ruby

# PVC: Easy as shell pipes
# https://rubygems.org/gems/pvc
require 'pvc'

# SoX: Sound eXchange
# http://sox.sourceforge.net/

destination_dir = 'amplified'

Dir.mkdir destination_dir unless Dir.exists? destination_dir

Dir.glob('./*.wav').each do |f|
  ratio_db = PVC.new("sox", f, "-n", "stat", "-v").run.stderr.chomp
  PVC.new("sox", "-v", ratio_db, f, "amplified/#{f}").run
end