Please check that you have enabled noise recording in Application settings → Sleep noise recording. Noise recording in not enabled by default as it causes slightly increased battery consumption during sleep tracking.
Next please check your Application settings → Sleep noise recording → Recording volume threshold you may want to lower your threshold in order to get more recordings, 20% is the default but 10% may be a better match for your device.
Also Application settings → Sleep noise recording → High quality recording is good to enabled as it features a better algorithm to capture significant noises.
Next try to adjust the recording threshold. You can start very low – for example 5/100…If you start sleep tracking you see a recording progress bar at the top. There are two indicators, one shows the actual threshold and the other the actual recorded level. When even the second line gets over the first line recording starts.
Please do a loud noise to calibrate the scale and then try to make a normal noise you would expect sleep talk would be during night. If you see your talking is getting recorded (red icon to the left) than you are setup. Otherwise please try to adjust the recording threshold.
In case you are still suffering issues please send us a debug report (Alarms tab → menu → send debug).