Repeated studies have confirmed that heterosexual women prefer deeper voices whispering sweet nothings in their ears. In addition to associating lower-pitched male voices with masculinity, women associate those bass notes with authority, larger body size and physical attractiveness [source: O'Luanaigh]. Fortunately for tenors out there, a recent Australian study at least debunked the notion that a deeper voice intimated superior sperm quality [source: Parry].
Perhaps since deeper-pitched voices have attracted such a sexy reputation, people may lower their registers when speaking to their special someones. In a 2010 study, male and female study participants were asked to record messages to be played for fictional recipients. Researchers showed individual participants photos of fictional message recipients; the more attractive participants rated the fictional recipients, the more likely they were to deepen their voices [source: PhysOrg]. But a conflicting study found that the more tantalizing the male face, the higher -- not lower -- women raised their vocal pitch [source: Fraccaro et al]. Either way, it seems we attempt to fine tune our voices to sound like sweet music to our beloveds' ears.