We stayed in the apartment for 4 nights including the weekend and although it is located in the center of Bairro Alto and therefore in the center of the bar scene of Lisbon with a lot of people passing by the apartment throughout the night we never had a problem sleeping because of any noise. The windows are pretty soundproof and the apartment itself was amazingly furnished and had everything you need even if you wanted to stay longer than 4 nights! Coffee, basic seasoning, dishwashing liquid, ... everything.
Any questions were answered right away and we were welcomed very friendly upon arrival. All in all we would definitely recommend staying here, if you're searching for an nice place to stay in the center of Lisbon!