Is what is said true, that a woman's voice is 'awrah?

The voice of a woman is not considered 'awrah' (private and unlawful to expose) in an absolute sense. Women used to complain and ask questions to the Prophet, peace and blessings be upon him, and to the Caliphs, and they would greet non-mahram men and return their greetings without any disapproval. However, it is not permissible for her to soften or break her voice in speech, as Allah Almighty says: (O wives of the Prophet, you are not like any other women. If you fear Allah, then do not be soft in speech [to men], lest he in whose heart is disease should covet, but speak with appropriate speech.) This is because such softness might entice men and become a temptation for them.