Question: 33:53 mentions that women must speak to men from behind a curtain. Please explain. 
    Answer: As far as 33:53 is concerned. it specifically concerns the house of the Prophet (sws) as is evident from the context. The context shows that the hypocrites at one time in Madinah had started raising scandals against the wives of the Prophet (sws). They would also suddenly barge into the house of the Prophet (sws) trying to catch the wives unaware and thereby try to scandalize their private lives. To safeguard against these scandal mongers, the Qur’an directed the wives to take certain precautionary measures. The wives of the Prophet (sws) were told that they should take care that whenever they have to say something to people in whose hearts there is the ailment of lewdness, they should speak without showing any softness to them:

O Wives of the Prophet! You are not like other women. If you fear Allah do not be too complaisant of speech lest one in whose heart is a disease should be moved with desire. (33:32) 

    Speaking from behind a curtain was another such measure, as the Qur’an says: 

If you ask his wives for anything, speak to them from behind the curtain. That is purer for your hearts and theirs. (33:53)

    Likewise, people who would assemble in the house of the Prophet (sws) were also directed to observe certain manners. They were told that they should not become a source of trouble for the residents of the house by coming at the wrong time or unnecessarily prolonging their stay. In the words of the Qur’an: 

O you who believe! enter not the Prophet’s dwellings unless permission be granted to you for a meal [and] not [so early as] to wait for its preparation. But if you are invited, enter and when you have eaten disperse. Linger not for conversation. Such behavior distresses the Prophet and he shows his regard for you but of the truth Allah does not have regard for anything. (33:53)

    So you can see that these directives have a specific background and cannot be extended to general application.