Peak normalization only looks at the absolute loudest point. RMS and LUFS (Loudness Units relative to Full Scale) measure human perception of loudness over time. Choose a tool that supports LUFS or Loudness Normalization for the most accurate results.
Have you ever watched a movie on your laptop and constantly adjusted the volume? One minute the dialogue is a quiet whisper. The next minute an explosion rattles your windows. This frustrating problem comes from uneven audio levels. sound normalizer portable