Singing during Nida:
It is forbidden for one to listen to his wife sing when she is in a state of Nida. [Therefore, the wife is to avoid singing in if her husband can hear her voice.]
During pure period: Even when one’s wife is pure, and it is permitted to listen to her sing, it is forbidden to learn Torah or Daven when she is singing.
 Pischeiy Teshuvah 195/10; Kitzur SH”A 153/10; Lechem Visimla 195/20; Kitzur Dinei Taharah 3/3; Shiureiy Sheivet Halevi p. 264; Sheivet Halevi 5/176
 Beir Sheva p. 119, brought in Kaf Hachaim 75/23; Elya Raba 75/5; Shaar Hatziyon 560/25; Piskeiy Teshuvos 75/12
 Admur 75/6; Rama 75/3; Ohel Moed 5/5; Hagahos Maimanis