Want to sound more authoritative or hit those low notes in your signature song? Just have a baby. It worked for Adele and Kristen Bell, who have both noted that during and after pregnancy, their voices were lower. Researchers at the University of Sussex in Britain may have an explanation, reports the Guardian. The investigators studied archive interview recordings of 20 mothers, including actresses, journalists, and singers, and compared them to a control group. Working from more than 600 voice recordings, they were able to analyze voice pitch in the five years before and after pregnancy and found that on average, a woman’s voice after giving birth dropped by 5%, which amounts to 44 hertz, or two musical notes. It's a noticeable difference, especially if you’re shooting to hit the low notes in an Oscar-winning theme song like Skyfall.
“When it comes to human voices, we can perceive pitch differences around 5 hertz in regular speech, so 44 hertz is a very salient difference,” lead author Dr. Kasia Pisanski tells the Washington Post. The experimental psychologist also notes that while singers have noticed their voices getting lower while pregnant, “the big drop actually happens after they give birth,” per the Guardian. The new range typically lasts for about a year. The researchers don’t know why this happens, but hormone changes may be partly responsible. It could also be partly behavioral. Studies show that people with low-pitched voices are generally viewed as more competent and dominant. So it’s possible that a woman might instinctively lower her voice to sound more authoritative when “faced with the new challenges of parenting,” says Pisanski. (Read more voice stories.)