Well... lol
Lisbon and Portugal are mostly silent at night. In case any of you haven't noticed it, Portugal is a state of law. There's a law of noise. To make noises at night there are only three possible scenarios:
1) The place (meaning the building) is inside\close to a special area, which has a special noise limit, like highways, avenues or the airport.
2) The place has a special temporary noise permit, with location, schedule, dates; this place has a new maximum noise limit allowed, licensed by the municipality. All densely populated municipalities in Portugal are obliged to publish its own "map of noise".
3) Some place or some people are out of order, that is, they are breaking the law. Too much noise at night. What the law says about it? Call the police. The police are allowed to take the necessary measures so the "noise producer" can stop at once the noise. Of course there are other kinds of inspections and other kinds of fines (light or heavy ones).
You don't need any earplugs to sleep - except if you're into any of those "special areas" or in case you're too sound sensitive.