Kol Isha

In an article entitled, "The Parameters of Kol Isha" by Rabbi Howard Jachter, the author cites the source for the prohibition.

"The Gemara (Berachot 24a) states, “The voice of a woman is Ervah, as the Pasuk [in Shir Hashirim 2:14] states ‘let me hear your voice because your voice is pleasant and appearance attractive.’” Rashi explains that the Pasuk in Shir Hashirim indicates that a woman’s voice is attractive to a man, and is thus prohibited to him. Rav Hai Gaon (cited in the Mordechai, Berachot 80) writes that this restriction applies to a man who is reading Kriat Shema, because a woman’s singing will distract him. The Rosh (Berachot 3:37) disagrees and writes that the Gemara refers to all situations and is not limited to Kriat Shema. The Shulchan Aruch rules that the Kol Isha restriction applies to both Kriat Shema (Orach Chaim 75:3) and other contexts (Even Haezer 21:2). The Rama (O.C. 75:3) and Bait Shmuel (21:4) clarify that this prohibition applies only to a woman’s singing voice and not to her speaking voice."

Ulitmately, Rabbi Jachter concludes, "Observance of the Kol Isha prohibition is quite challenging for us as this prohibition runs counter to the prevailing Western culture. In today’s promiscuous society where outrageous behavior is deemed acceptable, a woman’s singing voice appears innocuous. Moreover, the general culture views this prohibition offensive and demeaning to women. We are challenged to hold firm to our beliefs against the flow of the general cultural tide. This is one of the issues that we must part company with the rest of society, just as Avraham Avinu and Yitzchak Avinu parted with their two servants on the road to Akeidat Yitzchak. Rav Yehuda Amital told me that we should strictly observe the Kol Isha prohibition today precisely because of the deterioration of the moral standards of western society."

To read full article, click here.

In a response to a walkout of religious soldiers and officers at an IDF ceremony where women were singing, the following decision was taken.

"Religiously observant soldiers may not walk out of military assemblies to protest women singing, the Israel Defense Forces Chief of Staff's office has ruled. As an alternative, the soldiers may focus their eyes elsewhere, the office said."

http://www.haaretz.com/hasen/spages/1094887.html

The army's chief education officer found the walkout by the soldiers to be a "worrisome phenomenon" as it damaged group cohesion.

An article in today's Jpost quotes former Sephardi chief rabbi Mordechai Eliyahu answering a question posed to him as to what soldiers should do when their commanders order them to stay at an event in which a woman was singing.
"I told them - what should you do? The Talmud tells you… It is better you go to jail, disregard your commander and don't hear the voice of a woman singing."

Personally, I disagree with the decision taken by the IDF Chief of Staff's office. After all, there is an IDF rabbinate with a chief army rabbi responsible for making halachic decisions. It is up to him to call the shots regarding halacha and not for the chief education officer to trample on IDF soldiers' religious sensitivities.