What Does Normalizing Audio Do?
Normalizing changes the level of a file so it reaches a target. There are two kinds, and they answer different questions:
| Peak normalization | Loudness normalization | |
|---|---|---|
| Measures | The single loudest sample | Average perceived loudness (LUFS) |
| Typical target | −1 dB or 0 dB peak | −14, −16 or −23 LUFS |
| Makes files sound equally loud | No | Yes |
| Used by | Audio editors (Normalize effect) | Spotify, YouTube, podcast apps, broadcast |
The converter on this page uses loudness normalization (FFmpeg loudnorm, EBU R128), because that is what makes different tracks play at the same volume.
Why AAC Files Need Normalization
AAC files come from many sources — iTunes Store purchases at one loudness, Spotify downloads at another, iPhone voice memos at yet another. A mastered pop track might sit at -8 LUFS, while a podcast recording could be -20 LUFS. That's a 12 dB difference, making one sound roughly 2.5x louder than the other.
When you convert an AAC collection to MP3, these volume differences carry over. Normalization fixes this by adjusting every file to the same perceived loudness before encoding — no more reaching for the volume control between tracks.
Little extra quality loss: Normalization adjusts level before the MP3 encoding step, so it adds no second round of lossy compression. On very dynamic recordings the single-pass filter also evens out loud and quiet parts slightly (see below).
Which LUFS Target to Choose
Each platform has its own loudness standard. Here are the targets for the three presets available in the converter above:
| Preset | Target | True Peak | Best For |
|---|---|---|---|
| Podcast (-16 LUFS) | -16 LUFS | -1.5 dBTP | Apple Podcasts, spoken word, audiobooks |
| Streaming (-14 LUFS) | -14 LUFS | -1 dBTP | Spotify, YouTube, Tidal, Amazon Music |
| Broadcast (-23 LUFS) | -23 LUFS | -1 dBTP | EBU R128, European TV/radio |
Most common choice: If you're converting AAC files for Spotify or YouTube, use Streaming (-14 LUFS). For podcast episodes, use Podcast (-16 LUFS). Once the level is set, pick the best MP3 bitrate for podcasts to keep episode files small.
How Normalization Works During Conversion
When you upload an AAC file and select a normalization preset, CleverUtils performs two operations in a single pass:
- AAC → MP3 conversion: The AAC audio is decoded and re-encoded to MP3 using libmp3lame (VBR V2 by default)
- Loudness normalization: FFmpeg's
loudnormfilter analyzes the audio's integrated loudness (LUFS) and applies a constant gain adjustment to reach the target level
The filter runs in a single pass. In this mode loudnorm adjusts gain gradually through the file to hold the target loudness and loudness range (LRA 11, or 7 for Broadcast), so very dynamic recordings come out slightly more even. It does not change frequency response or the stereo image. A true peak ceiling (-1 or -1.5 dBTP, depending on the preset) prevents clipping.
Normalizing iTunes and Apple Music AAC Files
iTunes Store purchases are encoded at 256 kbps AAC with Apple's mastering standards. While individual tracks are well-mastered, albums from different eras and genres can still vary by 6–10 dB in loudness.
If you're converting an iTunes library to MP3 for a car stereo or portable player, normalization to -14 LUFS creates a consistent listening experience across your entire collection. The volume adjustment is tiny for most modern pop but significant for classical, jazz, and older recordings.
When Should You Normalize?
- Converting a mixed AAC library: Files from different sources (iTunes, rips, downloads) at different loudness levels. Normalize to -14 LUFS for consistent playback
- Preparing podcast episodes: AAC recordings from different microphones or environments. Normalize to -16 LUFS for Apple Podcasts compliance
- Uploading to Spotify or YouTube: These platforms normalize incoming audio anyway — delivering at the target loudness avoids platform-side adjustment
- Creating compilation playlists: Tracks from different albums and artists, all at different loudness. Normalization evens them out
For a deep dive into LUFS measurement, the EBU R128 standard, and platform-specific targets, see our complete LUFS guide. For choosing the right MP3 bitrate for your AAC files, see the bitrate guide.
Normalize vs Amplify vs Compress
- Amplify adds a fixed number of dB that you choose.
- Peak normalize calculates the gain for you, so the loudest peak lands on a target.
- Compress reduces the gap between loud and quiet parts. It changes dynamics, not just level.
- Order: if you compress, do it first and normalize last. Normalizing is the final level step, and compressing afterwards would move the level again.
How to Normalize Audio in Audacity, Premiere Pro and DaVinci Resolve
Audacity
Select the audio, then use Effect → Volume and Compression → Normalize for peak level, or Loudness Normalization for a LUFS target such as −14 or −16.
Premiere Pro
Right-click the clip and choose Audio Gain, then Normalize Max Peak to or Normalize All Peaks to and enter a value such as −1 dB.
DaVinci Resolve
Right-click the clip in the timeline and choose Normalize Audio Levels. Pick Sample Peak Program for a peak target, or a loudness standard (ITU-R BS.1770) for LUFS.
FFmpeg
The Streaming preset on this page runs: ffmpeg -i input.m4a -af loudnorm=I=-14:LRA=11:TP=-1.0 -codec:a libmp3lame -q:a 2 output.mp3