I live in Bombay (Mumbai), India. I'm planning to install sliding sound-proof windows in a room. There are two common types of window frames manufactured here; one is aluminium, and the other is PVC, which is some kind of plastic. I've had conflicting information about which is better. I was told one the one hand that plastic deteriorates under local conditions, which is mostly very hot and humid (the location is a stones throw from the Arabian Sea), except during the monsoons, when we get torrential rain.
On the other hand, I talked to someone who works for a company called Beautex, and the person insisted there was no problem, and that PVC is actually better from a sound-proofing perspective, though they did not offer any reasons why. They do sell PVC windows in India, as can be seen here.
Personally, I'd incline towards aluminium without further information, since I've never heard of aluminium deteriorating, and it is quite strong and durable.
So, the question is, which is preferable and why?
Addendum: Reading the question How can I prevent aluminum window frames from heating up when they're in full sun? made me wonder if sunlight heating up the aluminium will be an issue. The window frames will certainly be exposed to direct sunlight for part of the day, though I'm not sure how long. The windows do have small roofs above them, to help keep of the rain, which may help.
NOTE: This is the same room as shown in The best kind of tiles for using on floor and walls, though it now no longer looks as it did in this photo. Since that time the wooden windows have been removed, and the small roofs over the windows have also been replaced, though the new ones are of a similar size.
UPDATE: I eventually went with uPVC windows, not aluminium. After research, I discovered that there are uPVC windows which are manufactured that are suitable for Indian climate conditions, and they seemed to offer better soundproofing than the aluminum ones did. Possibly better insulation too.