All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His Slave and Messenger.
The woman’s voice is not ‘Awrah according to the most evident opinion of scholars, as previously explained in Fatwa 84462. Some of the early Muslims received knowledge and learned Hadeeth from women; please refer to Fatwa 82157.
As long as the woman abides by the Islamic dress code and the necessary Islamic manners, and the intention of the man is not to find pleasure in listening to her voice and he feels safe from temptation, then there is no harm in listening to her lectures. However, it is more prudent to avoid that so as to be on the safe side and to guard one’s religiosity, especially if the knowledge that she teaches can be acquired from male lecturers.
Allaah Knows best.