When AAC has to become WAV
WAV is the safest format for any tool that processes audio. Many speech-to-text services, call analysis programs and research tools ask for WAV input. Audio editors handle it faster than compressed files. Video editing software sometimes misreads raw AAC timing, which causes the sound to drift out of sync, while WAV stays locked to the picture. Hardware samplers, broadcast playout systems and old CD writing software also want WAV. Converting AAC to WAV solves all of these at once.
What happens to quality and size
The AAC is decoded to plain samples. No new loss is added, so the WAV sounds exactly like the AAC, but it also cannot sound better: whatever the AAC encoder removed stays removed. The size grows a lot:
| File | Data rate | Size of 10 minutes |
|---|---|---|
| AAC, 128 kbps | 128 kbps | about 9.6 MB |
| WAV, 16-bit, 44.1 kHz stereo | 1411 kbps | about 106 MB |
| WAV, 16-bit, 16 kHz mono | 256 kbps | about 19 MB |
Settings for common targets
- Audio editing: 16-bit, original sample rate, original channels.
- Video projects: 16 or 24-bit at 48 kHz, which is the standard rate in video.
- Speech recognition and transcription: many systems prefer 16 kHz mono, 16-bit. This keeps files small and matches what the recognition models expect.
- Audio CD: 16-bit, 44.1 kHz, stereo.
24-bit adds nothing for a file that came from AAC; use it only when your project requires 24-bit files.
Notes on raw AAC files
Raw .aac files sometimes start with a short burst of silence or noise, especially when they were cut from a radio stream. After converting, you can remove it in the audio editor. If the recording is of a call or meeting with background noise, the noise reduction tool works directly on the WAV. Since raw AAC has no tags, there is nothing to carry over to the WAV. If you prefer a smaller lossless file, AAC to FLAC keeps the same audio in about half the space.