"It's not just that we change the sound of our voice, but that others can easily perceive those changes," said Susan Hughes, associate professor of psychology Albright College, US.
The study looked at how individuals alter their voices, or engage in voice modulation, when speaking to romantic partners versus same-sex friends during brief telephone conversations.
Researchers recruited 24 callers who were newly in love and still in the so-called honeymoon period. Callers were asked to phone their romantic partners, as well as a close same-sex friend, and in both cases engage in a conversation asking specifically "how are you?" and "what are you doing?"
Researchers then played the recordings to 80 independent raters who judged the samples for sexiness, pleasantness and degree of romantic interest. Raters were exposed to only one end of the conversation and, in some cases, for only 2 seconds.
Still, raters were able to correctly identify, with greater than chance accuracy, whether the caller was speaking to a friend or lover, leading researchers to believe that people will alter their voice to communicate their relationship status.
"Vocal samples directed toward romantic partners were rated as sounding more pleasant, sexier and reflecting greater romantic interest than those directed toward same-sex friends," says the study.
Researchers also performed a spectrogram analysis on the samples to examine pitch and found that both men and women tend to mimic or match the pitch of their romantic partners. Women will use a lower pitch, while men will employ a higher one when speaking to their romantic partner.
According to the study, this effect represents desire for affiliation and intimacy and is a way to communicate affection.
"There was vulnerability associated with the voices of those newly in love. Perhaps people don't want to be rejected," said Hughes.
The study was published in the Journal of Nonverbal Behavior.