For Aizawa I'm looking for a very stoic sounding kind of voice, that of a serious mentor in around the mid-low to low range. He is voiced by Alex Organ! 

Character Description:

Shota is a very stern and mostly reserved man who has lofty expectations of his students. He is primarily moved by logic and does not believe in the necessity to maintain a clean-cut appearance or filter his words or ideas for others. He often comes off as cold, apathetic, and impatient and exhorts very little energy in most situations, preferring to take naps in his sleeping bag instead.[2][5]

As a teacher of high expectations, Shota is known to expel students who he feels are not suited for U.A. High. It is noteworthy that he has not expelled any students from Class 1-A yet despite being well known for doing so.[6] He can be rigid and strict when necessary, and also has little tolerance for disobedient behavior. Shota is not afraid of putting his students through rigorous training and often pushes the more unpleasant parts of Heroism so that his students can overcome their limits.

Shota has proven to be very vocal and unafraid when expressing his ideas. He has mentioned on several occasions that some of U.A.'s choices when it comes to examinations are not practical or challenging enough for real Hero hopefuls and is adamant about having certain systems used by the institution changed.[7] He also blatantly stated that he did not believe Izuku Midoriya could become a hero when they first met.[1] He is also known for lying to his students in order to manipulate them into giving their best, a technique he describes as a "logical ruse".[8]

Despite his apathetic traits, Shota genuinely cares about his students and will go to great lengths to protect them as he saved Tsuyu Asui from Tomura Shigaraki. He has also expressed belief in his students on multiple occasions and is confident that even the likes of Katsuki Bakugo would not be swayed by Villains. Recovery Girl even implied that he allowed himself to be captured by Momo Yaoyorozu during her End of Term Test in order to boost her confidence.[9]

Shota has shown on several occasions that he is not completely devoid of joy or humor. Despite his personality, he often grins whenever he is impressed by one of his students[1][9] or after he tricks them with one of his logical deceptions.[6][8]