What is the ruling on girls sending voice messages using their voices in mixed-gender groups when there is no necessity, what are the Sharia-related dangers resulting from that, and what are examples of necessity that permit it?

Young men and women should be in separate communication groups to avoid what is unlawful (haram) and temptation (fitna). If there is a need for a joint group, there is no harm in it, provided that Islamic guidelines are adhered to and temptation is avoided. If there is no need for a woman to send an audio clip in a group with non-mahram men, then she should not do so. However, if there is a need, there is no harm in it, provided that she avoids softening and alluring her voice. A woman's voice is not considered 'awrah (something that must be concealed) according to the more preponderant opinion, based on the Almighty's saying: "And when you ask [his wives] for something, ask them from behind a partition" and His saying: "then do not be soft in speech [to men], lest he in whose heart is disease should covet, but speak with appropriate speech."