What voice is heard?
Rashi citing Targum Yonasan: A voice is heard in the height of the world - the voice of Beis Yisrael crying over Yirmeyah ha'Navi, when Nevuzaradan sent him from Ramah to return from the exiles to Gedalyah ben Achikam, like it says below (40:5-6).
What is "Ramah"?
Malbim: It is a city in Binyamin 1 .
Radak: It is a high hill, so the voice will be heard from afar.
Rashi implies that it is the city from which Nevuzaradan sent Yirmeyah. Shoftim 4:5 implies that Ramah is in Har Efrayim. (PF)
Why is specifically Rachel's voice heard?
Rashi citing Eichah Rabah, Pesichah 24: The Avos and Imahos went to appease Hashem for Menasheh erecting an idol in the Heichal; He was not appeased. Rachel entered and said, whose mercy is greater - Yours or that of humans?! Yours is greater! I entered my rival into my house. All the Avodah that Yakov served My father was for me. When I came to enter the Chupah, they entered my sister. Not only was I silent (did not protect) - I even gave to her my Simanim! Also You - if Your children entered Your Tzarah in Your house, be silent to them! Hashem said, you defended them nicely - (verse 15) "there is reward for your action" and virtue, that you handed your Simanim over to your sister.
Radak: This is a metaphor for the 10 tribes, that their head was Efrayim. It mentions the mother of all of them 1 , i.e. Rachel, as if she cries for her children.
Radak: citing Bereishis Rabah 82:10: They were led to Galus on a road that passes by her grave. Why did Yakov bury her on the road to Efrat? He saw with Ru'ach ha'Kodesh that in the future, the exiles will pass there. Therefore he buried her there, in order to request mercy for them.
Malbim: It is as if she cries for her children, Yosef and Binyamin.
Why is Rachel the mother of all of them? Perhaps he means that since she is Efrayim's mother, it is as if she is the mother of all of them.
What is "Tamrurim"?
Radak: She cries with bitterness of heart, like it says "Amarer ba'Bechi" (Yeshayah 22:4), "u'Vachu Elayich b'Mar Nefesh" (Yechezkel 27:31).
Why does it say "Mevakah" (and not Bochah)?
Radak: The conjugation Mif'al shows great crying.
Why does it say twice "Al Baneha"?
Malbim: She cries for her children who went to Galus - Bnei Yosef and Binyamin. The latter will return in the days of Koresh. She refuses to be consoled for Bnei Yosef, who were exiled [among the 10 tribes] and will not return.
To what does "Einenu" apply?
Radak: The Am, i.e. the 10 tribes. Only Yehudah and Binyamin returned from Galus Bavel. The 10 tribes did not; it is not known where they are.
Malbim: Bnei Yosef, who were exiled [among the 10 tribes] and will not return.
