Temperature is the most underestimated factor. The body needs to drop its core temperature to initiate sleep. A cool room between 18 and 22 degrees Celsius promotes this. Darkness should be as complete as possible. Even small amounts of light suppress melatonin production.
Noise is highly individual. The key is consistency. A sleep environment that changes from night to night disrupts the conditioning your brain develops around sleep cues. Keep lighting, sound, and temperature predictable.