Is backbiting the wife and her sister's daughter a reason for jinn and devils to enter the house and for sounds to be heard in it, and what is the solution?

You must advise your wife and your niece gently and kindly, and explain to them the danger of backbiting, and that it is one of the major sins. If your wife does not respond to the advice, then abandon her in bed. If she still does not respond, then strike her with a non-bruising strike. As for the voices you hear, increase your remembrance of Allah Almighty, especially by reciting Surat Al-Baqarah, and supplicate to Allah to avert evil from you and protect you from the wickedness of human and jinn devils.