Chazal darshen on "Borachu Hashem Mal'achav Giburei Cho'ach Osei Devaro Lishmo'a b'Kol Devaro", that this is a reference to Bnei Yisrael saying na'aseh v'nishma and putting the asiya, the doing, before the understanding of mitzvos. The simple understanding is that Bnei Yisrael are creditied with accepting the Torah unconditionally without first asking to hear what that entailed. Yet, is that what is really going on? By analogy: imagine the King tells you that you were just selected to receive his most precious prize - are you willing to take it? Do you need to really ask what the prize is before saying yes? Kal v'chomer if the King is Hashem, who would obviously not command a Torah that was not for the good of mankind.
Explains the Sefas Emes: there are different paths to attain knowledge. We can come to knowledge purely as an intellectual endeavor, or we can come to knowledge through experience and action. Na'aseh v'nishma means knowledge springs from actions and experience, through hearing the kol of Hashem not just in the blatt gemara, but in asiyas hamitzvos as well. The Sefas Emes continues: The pasuk does not say "lishmo'a... b'devaro", but "lishmo'a b'kol devaro". The Zohar writes that kol is a higher, more pnimi experience than dibbur - kol is communication without words which transcends the limitations of language and its barriers. The intellectual experience of just learning Torah is listening to the words of the dvar Hashem, but the drawing the wisdom of Torah from the experience of life is to listen to the kol. "Hakol kol Ya'akov" - its is not the content of our words, but the sound of our voice, the essence of who we are, that is significant.
I would just add that the experience of mattan Torah is viewed by Chazal as a tikkun for the cheit of Adam haRishon. Adam's cheit is "ki shamata b'kol ishtecha" - the Ohr haChaim explains that it was not the reasoning and words of Chavah which convinced Adam to sin, but the tone and expression of her voice, the kol. (Perhaps this is why there is an issur of kol isha). Mattan Torah was the restoration of the kol to its rightful purpose in life.