Assalamualaikum warahmatullahi wabarakatuh to all friends.
This article entitled 'Etiquette of female speaking with the opposite gender' by Sheikh Muhammad Salih Al-Munajjid.
*******In brief, what the scholars have said about women voices is that they are not Awrah in and of themselves, and there is nothing wrong with listening to them when there is a need to do so, so they do not forbid listening to them, but certain conditions apply, as follows:
The woman should speak without elongating the words, making her voice soft, or raising her voice. It is Haram for a man to listen with enjoyment, for fear of Fitnah (temptation). The decisive factor for knowing what is Haram in the matter of womens speaking is what is included in the ayah (interpretation of the meaning):
"O wives of the Prophet! You are not like any other women. If you keep your duty (to Allah), then be not soft in speech, lest he in whose heart is a disease (of hypocrisy, or evil desire for adultery, etc.) should be moved with desire, but speak in an honorable manner. " [Noble Quran 33:32]
What is forbidden is being too soft in speech. It is obligatory for women to speak in an honorable manner, which means, that they should not make their voices soft when addressing men.
In conclusion, what is required of the Muslim woman when she speaks to a non-Mahram man is that she should adhere to what is mentioned in this Ayah.
1) She should refrain from what is forbidden and should fulfill her duties.
2) She should speak only when necessary, and only about matters that are permissible and honorable, not evil.
3) Between a woman and a non-Mahram man there should be no intonation, gestures, chat, joking, flirting or playful talk, so that there will be no room for provocation of desires and doubts.
4) Women are not prevented from talking to non-Mahram men when it is necessary to do so, such as dealing directly with them when buying things or conducting any other financial transaction, because in such cases it is necessary for both parties to speak.
5) A woman may also ask a scholar about some legal Islamic matter, or a man may ask a woman such questions, as is proven in various texts of the Quran and Sunnah.
Within the guidelines described above, there is nothing wrong with a woman speaking to a non-Mahram man.
And Allah knows best.