Prepare audio files for Unity: editing and import settings checklist

Most advice about audio in Unity starts with the import settings. They matter, but they cannot fix a file that starts with half a second of silence or ends with a click. This checklist covers both halves: what to do to the file, and how to import it.

Part 1: the file

Trim the silence

Sounds should start on their first audible sample and end when they have faded out. Silence at the start makes sounds play late; silence at the end breaks loops. In Unity, open the clips or their folder with Edit Audio and enable Trim Silence in Audio Tools to cut the dead air at both ends, then save trimmed copies. See removing silence.

Fade the cuts

Every hand-made cut that does not land at zero can click. A fade of a few milliseconds at each cut removes the click without changing the sound. Longer fade-outs belong at the end of music stingers and ambience loops. See fades.

Set the level

Quiet recordings and over-hot exports make mixing harder later. Bring each clip to a sensible peak with headroom, and match the perceived loudness of related sounds, such as all footsteps or all UI clicks. Audio Tools normalizes to a peak or to a loudness in LUFS, for a whole group in one pass. Peak level and loudness are different things; the article on peak and loudness normalization explains when each one helps.

Loop what loops

Ambience, engines and music beds need a loop point without a click or gap. Trim the silence first, then crossfade the end into the start; see seamless loops.

Choose a source format

Unity re-encodes every audio file on import, so the format of the source file mostly affects quality and repository size. WAV or AIFF is the safest source: lossless, sample-accurate and free of MP3 encoder padding. OGG is fine for long files. Avoid MP3 sources for loops; MP3 loop gaps explains why. Audio Tools converts to WAV in one step if a source needs it.

Keep the sample rate

There is rarely a reason to resample before import. Unity’s Sample Rate Setting can keep the rate, optimize it based on the highest frequency in the sound, or override it, for PCM and ADPCM compression. If a set of sources should share one rate anyway, the Output section in Audio Tools resamples copies to a rate between 48000 and 11025 Hz, and can also mix them to mono.

Part 2: the import settings

Select one or more clips and set these in the Inspector. Each platform can override them.

Load type

Unity’s documentation notes that decompressing Vorbis on load uses about ten times the memory of the compressed data, and ADPCM about three and a half times, so do not use Decompress On Load for long files.

Compression format

• PCM: full quality, largest size. Good for very short sounds where quality matters.
• ADPCM: smaller, with some noise that hides in noisy sounds such as footsteps, impacts and weapons.
• Vorbis: the most compact, with a quality slider. The usual choice for music, ambience and longer effects.

Channels

Force To Mono mixes a stereo clip down to one channel and then peak-normalizes it. Use it for positional 3D sounds, which Unity places with its spatializer anyway, and keep stereo for music and 2D ambience.

Preloading

Preload Audio Data loads the clip with the scene. Leave it on for sounds that must play instantly; turn it off for rarely used clips and load them with AudioClip.LoadAudioData when they are needed. Load In Background loads clips without blocking the main thread.

The whole checklist

1. Trim leading and trailing silence.
2. Fade every hand-made cut by a few milliseconds.
3. Set peaks with headroom, and match loudness within sound groups.
4. Crossfade the loop point of every loop.
5. Use WAV or AIFF sources, especially for loops.
6. Keep the source sample rate; let Unity optimize it if needed.
7. Pick the load type by length and frequency of use.
8. Pick the compression format by kind of sound.
9. Force mono for positional sounds.
10. Preload what must play instantly.

Steps 1 to 5 are where Audio Tools helps, for a whole folder at once and without leaving the Editor.