Alfama must be one of the most silent neighbourhoods in a capital. Due to its narrow streets, there is no traffic noise. You feel like in a village yet you are the center of a capital of a country. Since it is so silent, it is normal that you will hear when someone close by speaks or puts a machine on - but that's way nicer than typical traffic and street noise of most cities!
I stayed in the apartment many times myself and never heard a washing machine. I guess you were just unlucky to be there while the neighbors were making a major clean up - sorry about that.