[Steve King]

There are many free audio file converters. This one, https://www.nch.com.au/switch/index.html, will convert from .amr files to .wav files, which should do what you want.

[Steve King]

A brick wall limiter is a wonderful tool; however, if you use it indiscriminately it can drastically affect the dynamic range of your audio. Here’s how I use it. I examine the track or event that I want to conform to a specific maximum volume. I then raise or lower the overall track amplitude so that most of the peaks lie just below the maximum. That might involve a simple amplitude change or the application of a compressor. Then, as a last step, I apply the brick wall limiter to take care of those rogue peaks that fall above the max amplitude specification. I hear too many tracks that have been hammered to keep levels at spec, without regard to the aesthetic nature of the track. I don’t want all my tracks to sound like “Sunday! Sunday! US30 Drag strip!”