God help you if you moved to Spain for peace and quiet! Two old ladies waiting to be served in the local butchers can be ear-splitting, let alone your local karaoke bar. I doubt very much if more than 5% of all mopeds in Spain have silencers fitted, and most of our local buses probably would fail to meet whatever standards exist for controlling both air and noise pollution. Add to that the barking dog problem......
Where we live, there is a small garden opposite, which fills up on Friday and Saturday nights with youngsters doing the "botellon". The noise goes on 'till 3, 4 and 5 in the morning. When we ring the local police, they usually come out, and usually the crowd moves on. We got fed up with ringing, so went to the Town Hall to see what could be done. They were very sympathetic and helpful, asking us to fill out a denuncia specifically addressed the Mayor. Apparently, although the botellon is illegal, the police can not move them on unless they have somewhere else to go, and until the Mayor decides where that place should be, the police are virtually powerless to act. Can't quite figure that one out, but that's what we were told. We suggested the square outside the Mayor's house would be a good spot.
Late night noise does however seem to be a hot topic, as many bar owners will tell you. There are strict rules for new bar licence applications, but it seems to be taking a long time for established premises to be brought into line, although this varies a great deal from one region to another. For example, the Punta Ballena in Magalluf, which was once one of the roudiest night spots in Europe, is now so quiet after midnight, when all terraces must be taken in and double doors closed, that you can hear a pin drop. Bit silly really, since anyone with an apartment there either owns a bar or is drinking in one!
No idea what the law says on this issue; as you said, very difficult to actually get any info, but I found the following articles, which seem to suggest all is not lost:
From Sur in English, November 2004:
The European Court of Human Rights in Strasbourg has found Spain guilty of noise pollution, sentencing the authorities to pay damages to a plaintiff, Pilar Moreno, who lives in the centre of Valencia. The level of decibels recorded in her home at 3.30 a.m. on certain nights was double that permitted by law. This decision opens up the way for thousands of city dwellers affected by the racket made by young people drinking in the streets at night to sue town halls all over Spain.
Also found this, dated February 2007:
Zaragoza Town Hall has been ordered to pay a total of €385,000 in compensation to fifty-five residents, who will each receive €7,000. The ruling of the court, against which the Town Hall has the right to appeal, finds the council guilty of failing in its duty to control noise levels in the city centre popular night-spot zone (photo). According to the president of the residents association that brought the case, Ignacio Sáenz de Cosculluela, the ruling also means the onus will no longer be on complainants to provide evidence when bringing similar cases in the future and obliges the council to ensure no further breaches of exisiting noise pollution legislation.
And this, March 2007:
The regional government of Murcia is preparing a decree which will oblige Town Halls in the Region to implement measures to control noise pollution. They will include drawing up a ‘noise map,’ setting out maximum decibel levels for all areas of the town, according to their location.
It follows a recent ruling by a judge in the Canary Islands, where the Santa Cruz de Tenerife carnival was temporarily halted when local residents complained about the noise.