[tjalfi]

Here are the two studies that are quoted by most of the articles on this topic.

The first is Does social desirability bias favor humans? Explicit–implicit evaluations of synthesized speech support a new HCI model of impression management[0]. This study found that both men and women interpret female voices as warmer.

The second is Are Computers Gender-Neutral? Gender Stereotypic Responses to Computers[1]. This study found that male voices are preferred when discussing computers and female voices are preferred when discussing relationships.

[0] http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.669...

[1] http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.536...