Using 16-bit for audio files is useful for keeping audio file sizes down. You may want to use 16‑bit for sessions with few tracks, and little mixing and plug-in processing. CDs (Compact Discs) use 16-bit.
Using 24-bit for audio files is commonly used for most music production and post-production sessions with multiple audio tracks, mixing, and plug-in processing. 24-bit files take up a third as much space as 16-bit files.
Using a 32‑bit floating point bit depth for audio files in Pro Tools sessions can help avoid clipping or unnecessary dithering with AudioSuite rendering. It can also help avoid rounding errors in signal processing (which can occur during bit-depth conversion for file playback and real-time plug-in insert processing). However, 32-bit files take up a third more disk space and audio streaming bandwidth, which can be problematic with higher track counts when using slower hard drives.
You can change the bit depth for all newly recorded or imported (and converted) files in the session by selecting a different
Bit Depth option in the Session Setup window.