Considerations in Recording - warnikchow/kosp2e GitHub Wiki
Record with mobile phone in in-door with minimized noise. Be aware of stationary noises (fridge, fan, etc.).
Sit on a chair and place a mobile phone on the table at a distance of 30cm from the mouth.
The length of the delay before/after the recording is not crucial, but the onset and offset of voice before and after the file start and end should not be too tight.
Keep the sampling rate at 44.1K (recommended). 16K is allowed. For file format, .wav is recommended. However, .mp3, .flac, and .aac are also allowed.