Is it unlawful for a woman to teach a language using her voice via a blog accessed by men, without direct communication, and must she close it to please her husband, or can she continue spreading knowledge?

A woman's voice is not awrah (private/uncovered) in itself. However, it becomes forbidden if it involves softness and coquetry in speech to one whose heart harbors illness (i.e., lust), and a woman has been prohibited from certain matters, such as the adhan (call to prayer), leading men in prayer, and delivering sermons, as a preventative measure against fitnah (temptation).

There is no softness or coquetry in the questioner's voice. Nevertheless, a woman should not make her voice heard by men except out of necessity, and general language instruction is not considered a necessity.

A wife must obey her husband in matters that do not involve disobedience (to Allah), and she should cease giving voice-based instruction to men. The questioner can teach women only in private voice rooms designated for them, as this fulfills her desire and does not cause embarrassment to her husband.