From a piece by R’ Gil student-
1. Berachos 24a
Rav Yitzchak said: A tefach of a woman is nakedness (‘ervah).
For what? If you say for looking at it, Rav Sheshes said: Why did the Torah count outer ornaments with inner ornaments? To tell you that anyone who looks at the small finger of a woman is as if he looked at the obscene place. Rather, [Rav Yitzchak is talking about] one’s wife an kerias shema.
Rav Chisda said: The thigh of a woman is nakedness as it says (Isaiah 47:2) “expose a thigh to cross a river” and it says (ibid. 3) “your nakedness will be exposed and your embarrassment will be seen.”
Shmuel said: The voice of a woman is nakedness as it says (Song of Songs 2:14) “for your voice is sweet and your countenance comely.”
Rav Sheshes said: The hair of a woman is nakedness as it says (ibid. 4:1) “you hair is like a flock of goats.”
2. Kiddushin 70a
[Rav Nachman said to Rav Yehudah]: Would you like to send regards to Yalta [Rav Nachman’s wife]?
He [Rav Yehudah] said: Shmuel said: The voice of a woman is nakedness.