Upholstery and egg crate type foams will not be rigid, and may not be flame retardant. EPS and XPS construction insulation foam are lighter weight, more rigid, and could be covered with batting and fabric. They come in 4'x8' sheets, but can be cut with a utility knife into smaller sizes. They are available from a big box home improvement store like HD or Lowes. Not sure if they are flame retardant. Depending on how large a piece you are mounting, I would think they may be light enough in weight that they could be mounted to the wall with 3M removeable hangers of some sort.

Are you able to make changes to the flat ? One very good way reduce noise from the street is to replace the windows with new windows with 2 or 3 layers of glass in well sealed new window frames. Another way is to add a layer of drywall to the front wall with an airspace between the original wall and the new drywall panels using a metal channel. If it is a rental and you can't make changes, keeping the windows closed is the best thing that you can do.

Following are my comments : 1.Buying cheaper branded sanitary fittings is only possible when you buy the same in bulk quantities. But I would like to highlight that these are one of the most important fixtures in the stated space. Don't compromise on the quality of it if you want them to survive the long run.(You can go for the Jaquar continental series or change to Parryware) You can certainly compromise on the WC & the WB since even brands like Somany give good ceramic fixtures at relatively low cost. There you can save your bucks. 2. I haven't worked on PVC vanity but can comment that marine ply cabinets also stand well for the wear and tear. 3. You can go ahead with just the glass partition avoiding the cubicle door. 4. Yes you can but the selection should be on the lighter side of the colour palette so that the bathroom should not look more claustrophobic due to its small size(2 m x 3.5m which is normal in today's real estate market in mumbai). Ar. Amol Bhopi AVB Architecture Mumbai 71.

Unpolished, unfinished wood planks, glass wool (use as last resort), or nylon fiber are three alternatives which can be used to seal gaps. Thickness of floors, walls also matters for sound to radiate through. Cheapest alternative is of course paper as the best sound absorbent paper. Unlaminated newsprint is the best.