The WHO European night-noise guidance uses 40 dB Lnight as a long-term target for protecting sleep and health. This is an environmental planning guideline, not a personal diagnostic threshold.
Yuelu shows night-noise context only when the device has a sufficiently complete overnight record. Compare repeated nights and consider the room, device placement, and other sources of measurement variation.
Original source
WHO Regional Office for Europe, Night noise guidelines for Europe. Read the guideline.
Interpretation note
An isolated higher reading should not be treated as proof that sleep was harmed. If noise repeatedly disrupts sleep, reducing exposure and discussing persistent problems with a professional may help.