Is a woman's voice considered 'awrah, and is it forbidden for her to speak in the presence of non-mahram men except out of necessity?

We have previously clarified in numerous fatwas that the preponderant opinion is that a woman's voice is not awrah (nakedness that must be covered), and that it is permissible for a woman to speak in the presence of a non-mahram man, or for him to hear her voice, provided certain conditions are met. However, despite all this, your sisters should not raise their voices when speaking in the presence of this non-mahram man, because this contradicts the modesty and shyness that a woman should embody, and it might also be a means for him to be tempted.