One of the more researched areas of voice and speech is the distinction between male versus female voices and speech patterns.  Much work has gone into both analyzing the differences and attempting to apply these findings into practice to change the perceived "sex" of the listener.  Let's talk a little about what has been discovered so far! Sex-Based Differences Determined From Conception Biology plays the primary role in determining how our voice and speech sound, and it starts at conception.  Once the human embryo's sex is determined as either "male" or "female" based on chromosomes, a cascade of changes occur at around 8 weeks gestational age (in the womb), including development of genitalia as well as dormant developmental instructions stored within our DNA that will later direct the development of secondary sex characteristics (including sex-based differences of the upper airway and vocal tract). The precise timing of an embryo