5:15 One may not discuss Torah or other holy matters in the sight of genitals, neither his own nor another person’s, even a child’s. (The one obvious exception is at a bris.) Closing one’s eyes is not sufficient so long as it is in front of him; rather, a person should turn away so that he is no longer facing the nudity. The Rema rules that in a case of need, we may be lenient when in sight of the nudity of a boy under nine or a girl under three (OC 75:4).
5:16 Any part that women traditionally cover, if a handbreadth is uncovered, a man may not recite holy words in sight of them. (A handbreadth is about 3 inches.) This includes the hair of a married woman and the sound of a woman singing. Other women, however, may pray and learn in sight of these things. If there is a woman singing and there’s no way for the man to avoid it, he may study and pray, being extra careful to concentrate on his learning or davening and not on the singer.