If you can put a 2nd door of glass or plastic,over the old door.
Double glazed windows will cut much of the noise, if correctly fitted. If you already have double glazing, then get a fitter to re-check the installation thoroughly as small gaps and misalignments can easily allow a lot of noise through past the frame. Cheap double glazing will also always have hollow frames which allow noise to pass through almost unhindered, so as long as you don't gum up any mechanisms you can have them injected with expanding foam filler like better quality frames have. better quality double glazing also uses thicker glass and the air-gap between the panes is carefully engineered to maximise insulation qualities. Although the aim is to maximise thermal insulation, a properly designed gap also improves acoustic insulation.
Insulation boards are a bit of a clumsy and unsightly idea, but you could use them to build internal or external window shutters. Heavy, full-length curtains (US= drapes) can also help. In the worst cases I have installed either triple glazed windows (expensive, but compact and very effective) or a second set of double glazed windows behind the outer set (bulky, slightly awkward, but less expensive than triple glazing, and gives more security but also harder to escape through in an emergency).
Other measures are to use sound absorbent materials in the room, so carpets instead of bare floors. If there's a balcony outside, then a screen of plants can help as well.
Don't assume that the walls are impervious either, many modern construction methods really allow the noise through especially if you live in an area with a warm climate. getting the wall cavities filled can help as can the construction of a curtain wall (battens screwed onto insides of existing outer wall, insulation board laid between the battens and then insulating plasterboard fixed on top to form new inner wall surface).
You won't kill the noise completely, but you can reduce it and what remains can have the quality improved so that it's less annoying.
Go to lowes or contact your broker