Why are male and female voices distinctive?

Are you asking what makes male voices lower than female voices? If that is your question, it's pretty simple. Testosterone causes the vocal folds to grow longer and thicker. read more

Female voices also tend to sound more cautious and tentative, for example by ending a statement with a raise in pitch, as if it were a question. Typical male voices strive to sound confident. Another essential factor, which is significantly harder to manipulate, is resonance: male voices have a distinctive resonant quality. read more

In a normal female this gap is usually pretty small, but it can contribute to what we perceive as a feminine voice. Think of the women's voices they use for "sexy" late night advertising - they exaggerate the breathy quality of female voices to sound more feminine. read more