Why M4A Files Have Inconsistent Volume
M4A is a container format — the loudness of each file depends entirely on how it was recorded or mastered. Here's why your M4A collection sounds uneven:
| M4A Source | Typical Loudness | Why |
|---|---|---|
| Modern pop (iTunes) | -8 to -12 LUFS | Loudness war — heavily compressed masters |
| Classical music | -20 to -28 LUFS | Wide dynamic range preserved |
| iPhone Voice Memos | -18 to -30 LUFS | Varies by recording distance and environment |
| Podcast recordings | -14 to -20 LUFS | Depends on mic setup and post-processing |
| GarageBand exports | -10 to -18 LUFS | Depends on mixing decisions |
That's a potential 20+ dB spread between your quietest Voice Memo and loudest pop song. Without normalization, converting these to WAV carries the volume inconsistency straight through.
Which LUFS Target to Choose
The converter above offers three normalization presets. Choose based on what you'll do with the WAV files:
| Preset | Target | True Peak | Best For |
|---|---|---|---|
| Podcast (-16 LUFS) | -16 LUFS | -1.5 dBTP | Voice Memos for podcast editing, spoken word |
| Streaming (-14 LUFS) | -14 LUFS | -1 dBTP | Music for DAW editing, consistent library playback |
| Broadcast (-23 LUFS) | -23 LUFS | -1 dBTP | EBU R128, European TV/radio production |
Most common choice: Use Streaming (-14 LUFS) when converting iTunes music or mixed content to WAV for editing. Use Podcast (-16 LUFS) for Voice Memos and spoken word recordings.
How Normalization Works
When you upload an M4A file and select a normalization preset, Convertio performs two operations in a single pass:
- M4A → WAV conversion: The AAC audio is decoded and written as uncompressed PCM (WAV)
- Loudness normalization: FFmpeg's
loudnormfilter measures the audio's integrated loudness (LUFS) and applies a constant gain adjustment to reach the target
The normalization is linear — a single gain value applied uniformly across the entire file. It does not compress dynamics, alter frequency response, or change the stereo image. A true peak limiter prevents clipping if the gain boost would push any peaks above the safe ceiling.
Why WAV output? Normalizing to WAV (instead of MP3) means the gain adjustment is applied without any lossy re-encoding. The result is uncompressed PCM audio — perfect for editing in Audacity, Pro Tools, Logic, or any DAW.
Normalizing iPhone Voice Memos
Voice Memos are one of the most common M4A files people convert. The challenge: each recording was captured at a different distance from the mic, in a different room, with different background noise levels. The result is wildly inconsistent volume.
Normalization solves this. Convert all your Voice Memos with the same LUFS preset, and every WAV file will play at the same perceived loudness:
- For podcast editing: -16 LUFS (matches Apple Podcasts requirements)
- For general editing: -14 LUFS (consistent baseline for any project)
- For transcription: -14 LUFS (clear, consistent playback volume)
Share Voice Memos to your Files app, then upload the .m4a files to the converter above. Each file will be normalized to your chosen target, regardless of how loud or quiet the original recording was.
Normalizing an iTunes Library
If you're converting iTunes M4A purchases to WAV for CD burning or DAW editing, normalization evens out the volume differences between albums. A 2024 pop album mastered at -8 LUFS and a 1990s recording at -16 LUFS will both end up at your chosen target.
Apple's built-in "Sound Check" feature does something similar during playback, but it doesn't modify the files. When you convert with normalization in Convertio, the loudness adjustment is baked into the WAV — no playback software required.
Normalization vs compression: Normalization = volume knob (preserves dynamics). Dynamic compression = squashes dynamics (loud parts get quieter, quiet parts get louder). Convertio uses only normalization — your audio's natural dynamics are never altered.
When Should You Normalize?
- Voice Memo collection: Multiple recordings at varying distances and environments. Normalize to -14 or -16 LUFS for consistent editing
- iTunes library to WAV: Albums mastered at different loudness levels. Normalize to -14 LUFS for even playback
- Podcast production: Voice Memos destined for podcast episodes. Normalize to -16 LUFS for Apple Podcasts compliance
- Video editing: M4A audio tracks from different sources. Normalize for consistent volume in your timeline
- CD burning: Songs from different albums. Normalize so CD tracks play at consistent volume
For a deep dive into LUFS measurement and the EBU R128 standard, see our complete LUFS guide. For choosing WAV quality settings (sample rate, bit depth, channels), see the WAV quality settings guide.