The Dropout shows Elizabeth Holmes deepening her voice. Why women do it – to sound like a man and convey authority and strength, an expert says

• The third episode of the series about the fallen tech exec shows her lowering the pitch of her voice. It’s done to convey competence and leadership, experts say
• If the Theranos founder did intentionally modify her voice tone, she would not be alone – Britain’s first woman prime minister, Margaret Thatcher, took lessons