> For the complete documentation index, see [llms.txt](https://docs.facephi.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.facephi.com/docs.facephi-en/sdks/backend-sdk/voice/technical_documentation/recommendations.md).

# Recommendations

## 1. Recommendations for the enrollment process

* The secret phrase must be phonetically rich.
* The secret phrase must never be a repetition of words.
* The secret phrase must be spoken in the user's natural tone (\*).

(\*) The registration should not be carried out if the user has a cold or in environments where audio is restricted.

## 2. Best practices

The registration should be updated every two years due to the natural change in the voice.

## 3. Situations that reduce the system's reliability

The following conditions significantly affect the algorithm:

* Aggressive audio compression.
* Noise-canceling hardware.
* Downsampling of frequencies below 16 kHz.