The effect was small, but, nonetheless quite interesting. If semen quality is linked to the probability of a pregnancy per copulation, and if voice attractiveness is linked to the expected number of copulations, then it's easy to see how a tradeoff between voice attractiveness and semen quality might work.6(12): e29271. doi:10.1371/journal.pone.0029271Leigh W. Simmons et al.Women find masculinity in men's faces, bodies, and voices attractive, and women's preferences for men's masculine features are thought to be biological adaptations for finding a high quality mate. Fertility is an important aspect of mate quality. Here we test the phenotype-linked fertility hypothesis, which proposes that male secondary sexual characters are positively related to semen quality, allowing females to obtain direct benefits from mate choice. Specifically, we examined women's preferences for men's voice pitch, and its relationship with men's semen quality.These data are more consistent with a trade off between sperm production and male investment in competing for and attracting females, than with the phenotype-linked fertility hypothesis.