New mothers’ voices will temporarily deepen following the birth of a child, scientists have claimed.
Researchers from the University of Sussex found that after pregnancy, women’s voices will drop by more than two musical notes and become more monotonous after having their first baby.
However, according to the study, this ‘masculinising effect’ is not permanent with voices tending to revert back to their previous pitch after one year.
Scientists speculated that this change could be hormonal, or an attempt by the mums to sound more authoritative in response to their new role of parent.
Lead researcher Dr Kasia Pisanski, of the University of Sussex’s School of Psychology, said: ‘Our results show that, despite some singers noticing that their voices get lower while pregnant, the big drop actually happens after they give birth.’
The study looked at 20 mothers, including singers, actresses, celebrities and journalists, and compared them to a control group.
Archive interview footage from five years before and after pregnancy was analysed, with researchers finding women’s average voice pitch had dropped by over five per cent – the equivalent of 1.3 semitones.
The highest pitch in the group also dropped by an average of 2.2 semitones, or more than two notes, and they had less variation in pitch, the study found.
Dr Kasia added: ‘Our results demonstrate that pregnancy has a transient and perceptually salient masculinising effect on women’s voices.
‘One possible explanation is that this is caused by hormone changes after childbirth.
‘Previous research has shown that women’s voices can change with fertility, with pitch increasing around the time of ovulation each month, and decreasing following menopause.’
She added: ‘We know that after pregnancy, there’s a sharp drop in the levels of key sex hormones, and that this could influence vocal fold dynamics and vocal control.
‘This effect could also be behavioural. Research has already shown that people with low-pitched voices are typically judged to be more competent, mature, and dominant, so it could be that women are modulating their own voices to sound more authoritative, faced with the new challenges of parenting.’
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Singer Adele revealed at a concert in Sydney last year that her voice became ‘a lot lower’ when she was pregnant with her son, Angelo.
She asked the crowd to ‘bear with’ her because she was struggling to reach the low notes in her Oscar-winning song Skyfall, as she wrote it when she was pregnant. She recently revealed that her voice is only now returning to its pre-pregnancy level.